Build a content builder agent

Build a content writing agent with brand memory, skills, subagents, and image generation

Overview

This guide demonstrates how to build a content writing agent from scratch using Deep Agents.

The agent you build will:

1. Load voice and workflow rules from AGENTS.md and skill folders
2. Delegate web research to a specialized subagent with web_search
3. Draft blog or social content following the loaded skill
4. Generate cover or social images with Gemini and save files under the project directory

The code in this tutorial wires in image generation tools and a filesystem backend so the agent can read and write posts, research notes, and images under the project directory. For the full runnable project, see the content-builder-agent example.

Key concepts

This tutorial covers:

• Long-term memory for TODO
• Skills for TODO
• Subagents for TODO
• Filesystem backends for file read and write
• Custom tools for search and image generation

Prerequisites

API keys:

• Anthropic (Claude) or other provider API key
• Google (Gemini) for image generation with gemini-2.5-flash-image
• Tavily for web search (free tier)
• LangSmith for tracing (optional)

Node.js 18 or later.

Setup

1. Create project directory

   mkdir content-builder-agent
   cd content-builder-agent
   
2. Install dependencies

   npm

   npm install deepagents @langchain/core @langchain/anthropic @google/generative-ai tavily zod tsx
   

   yarn add deepagents @langchain/core @langchain/anthropic @google/generative-ai tavily zod tsx
   

   Add tsx to run content_writer.ts. The --input-type=module flag applies only to --eval, --print, or stdin, not to a script file path.

   Install @langchain/anthropic so LangChain can load the default Claude model that createDeepAgent uses.

3. Set API keys

   export ANTHROPIC_API_KEY="your_anthropic_api_key"
   export GOOGLE_API_KEY="your_google_api_key"
   export TAVILY_API_KEY="your_tavily_api_key"           # Optional
   export LANGSMITH_API_KEY="your_langsmith_api_key"     # Optional
   

Add configuration files

The example keeps behavior in three kinds of files: memory, skills, and subagent definitions.

1. Add AGENTS.md

   Create AGENTS.md in the project root. When you later create the agent and specify this file as part of the memory parameter, it gets loaded this into the system prompt so brand voice and research expectations apply to every run.

   # Content Writer Agent
   
   You are a content writer for a technology company. Your job is to create engaging, informative content that educates readers about AI, software development, and emerging technologies.
   
   ## Brand Voice
   
   - **Professional but approachable**: Write like a knowledgeable colleague, not a textbook
   - **Clear and direct**: Avoid jargon unless necessary; explain technical concepts simply
   - **Confident but not arrogant**: Share expertise without being condescending
   - **Engaging**: Use concrete examples, analogies, and stories to illustrate points
   
   ## Writing Standards
   
   1. **Use active voice**: "The agent processes requests" not "Requests are processed by the agent"
   2. **Lead with value**: Start with what matters to the reader, not background
   3. **One idea per paragraph**: Keep paragraphs focused and scannable
   4. **Concrete over abstract**: Use specific examples, numbers, and case studies
   5. **End with action**: Every piece should leave the reader knowing what to do next
   
   ## Content Pillars
   
   Our content focuses on:
   - AI agents and automation
   - Developer tools and productivity
   - Software architecture and best practices
   - Emerging technologies and trends
   
   ## Formatting Guidelines
   
   - Use headers (H2, H3) to break up long content
   - Include code examples where relevant (with syntax highlighting)
   - Add bullet points for lists of 3+ items
   - Keep sentences under 25 words when possible
   - Include a clear call-to-action at the end
   
   ## Research Requirements
   
   Before writing on any topic:
   1. Use the `researcher` subagent for in-depth topic research
   2. Gather at least 3 credible sources
   3. Identify the key points readers need to understand
   4. Find concrete examples or case studies to illustrate concepts
   

   To make this agent comply with your own tone, pillars, and formatting rules, update the text in AGENTS.md.

2. Add skills

   Create a skills/ directory. Each skill is a folder containing a SKILL.md file with YAML frontmatter (name, description) and instructions for the skill.

   Create skills/blog-post/SKILL.md and copy the following text into it which contains information on crating long-form posts, optimizing content for SEO, and generating cover images.

   ---
   name: blog-post
   description: Writes and structures long-form blog posts, creates tutorial outlines, and optimizes content for SEO with cover image generation. Use when the user asks to write a blog post, article, how-to guide, tutorial, technical writeup, thought leadership piece, or long-form content.
   ---
   
   # Blog Post Writing Skill
   
   ## Research First (Required)
   
   **Before writing any blog post, you MUST delegate research:**
   
   1. Use the `task` tool with `subagent_type: "researcher"`
   2. In the description, specify BOTH the topic AND where to save:
   
   ```
   task(
       subagent_type="researcher",
       description="Research [TOPIC]. Save findings to research/[slug].md"
   )
   ```
   
   Example:
   ```
   task(
       subagent_type="researcher",
       description="Research the current state of AI agents in 2025. Save findings to research/ai-agents-2025.md"
   )
   ```
   
   3. After research completes, read the findings file before writing
   
   ## Output Structure (Required)
   
   **Every blog post MUST have both a post AND a cover image:**
   
   ```
   blogs/
   └── <slug>/
       ├── post.md        # The blog post content
       └── hero.png       # REQUIRED: Generated cover image
   ```
   
   Example: A post about "AI Agents in 2025" → `blogs/ai-agents-2025/`
   
   **You MUST complete both steps:**
   1. Write the post to `blogs/<slug>/post.md`
   2. Generate a cover image using `generate_image` and save to `blogs/<slug>/hero.png`
   
   **A blog post is NOT complete without its cover image.**
   
   ## Blog Post Structure
   
   Every blog post should follow this structure:
   
   ### 1. Hook (Opening)
   - Start with a compelling question, statistic, or statement
   - Make the reader want to continue
   - Keep it to 2-3 sentences
   
   ### 2. Context (The Problem)
   - Explain why this topic matters
   - Describe the problem or opportunity
   - Connect to the reader's experience
   
   ### 3. Main Content (The Solution)
   - Break into 3-5 main sections with H2 headers
   - Each section covers one key point
   - Include code examples, diagrams, or screenshots where helpful
   - Use bullet points for lists
   
   ### 4. Practical Application
   - Show how to apply the concepts
   - Include step-by-step instructions if applicable
   - Provide code snippets or templates
   
   ### 5. Conclusion & CTA
   - Summarize key takeaways (3 bullets max)
   - End with a clear call-to-action
   - Link to related resources
   
   ## Cover Image Generation
   
   After writing the post, generate a cover image using the `generate_cover` tool:
   
   ```
   generate_cover(prompt="A detailed description of the image...", slug="your-blog-slug")
   ```
   
   The tool saves the image to `blogs/<slug>/hero.png`.
   
   ### Writing Effective Image Prompts
   
   Structure your prompt with these elements:
   
   1. **Subject**: What is the main focus? Be specific and concrete.
   2. **Style**: Art direction (minimalist, isometric, flat design, 3D render, watercolor, etc.)
   3. **Composition**: How elements are arranged (centered, rule of thirds, symmetrical)
   4. **Color palette**: Specific colors or mood (warm earth tones, cool blues and purples, high contrast)
   5. **Lighting/Atmosphere**: Soft diffused light, dramatic shadows, golden hour, neon glow
   6. **Technical details**: Aspect ratio considerations, negative space for text overlay
   
   ### Example Prompts
   
   **For a technical blog post:**
   ```
   Isometric 3D illustration of interconnected glowing cubes representing AI agents, each cube has subtle circuit patterns. Cubes connected by luminous data streams. Deep navy background (#0a192f) with electric blue (#64ffda) and soft purple (#c792ea) accents. Clean minimal style, lots of negative space at top for title. Professional tech aesthetic.
   ```
   
   **For a tutorial/how-to:**
   ```
   Clean flat illustration of hands typing on a keyboard with abstract code symbols floating upward, transforming into lightbulbs and gears. Warm gradient background from soft coral to light peach. Friendly, approachable style. Centered composition with space for text overlay.
   ```
   
   **For thought leadership:**
   ```
   Abstract visualization of a human silhouette profile merging with geometric neural network patterns. Split composition - organic watercolor texture on left transitioning to clean vector lines on right. Muted sage green and warm terracotta color scheme. Contemplative, forward-thinking mood.
   ```
   
   ## SEO Considerations
   
   - Include the main keyword in the title and first paragraph
   - Use the keyword naturally 3-5 times throughout
   - Keep the title under 60 characters
   - Write a meta description (150-160 characters)
   
   ## Quality Checklist
   
   Before finishing:
   - [ ] Post saved to `blogs/<slug>/post.md`
   - [ ] Hero image generated at `blogs/<slug>/hero.png`
   - [ ] Hook grabs attention in first 2 sentences
   - [ ] Each section has a clear purpose
   - [ ] Conclusion summarizes key points
   - [ ] CTA tells reader what to do next
   

   Next, create skills/social-media/SKILL.md and copy the following text into it which contains information on drafting social media posts and generating accompanying imagery:

   ---
   name: social-media
   description: Drafts engaging social media posts, writes hooks, suggests hashtags, creates thread structures, and generates companion images. Use when the user asks to write a LinkedIn post, tweet, Twitter/X thread, social media caption, social post, or repurpose content for social platforms.
   ---
   
   # Social Media Content Skill
   
   ## Research First (Required)
   
   **Before writing any social media content, you MUST delegate research:**
   
   1. Use the `task` tool with `subagent_type: "researcher"`
   2. In the description, specify BOTH the topic AND where to save:
   
   ```
   task(
       subagent_type="researcher",
       description="Research [TOPIC]. Save findings to research/[slug].md"
   )
   ```
   
   Example:
   ```
   task(
       subagent_type="researcher",
       description="Research renewable energy trends in 2025. Save findings to research/renewable-energy.md"
   )
   ```
   
   3. After research completes, read the findings file before writing
   
   ## Output Structure (Required)
   
   **Every social media post MUST have both content AND an image:**
   
   **LinkedIn posts:**
   ```
   linkedin/
   └── <slug>/
       ├── post.md        # The post content
       └── image.png      # REQUIRED: Generated visual
   ```
   
   **Twitter/X threads:**
   ```
   tweets/
   └── <slug>/
       ├── thread.md      # The thread content
       └── image.png      # REQUIRED: Generated visual
   ```
   
   Example: A LinkedIn post about "prompt engineering" → `linkedin/prompt-engineering/`
   
   **You MUST complete both steps:**
   1. Write the content to the appropriate path
   2. Generate an image using `generate_image` and save alongside the post
   
   **A social media post is NOT complete without its image.**
   
   ## Platform Guidelines
   
   ### LinkedIn
   
   **Format:**
   - 1,300 character limit (show more after ~210 chars)
   - First line is crucial - make it hook
   - Use line breaks for readability
   - 3-5 hashtags at the end
   
   **Tone:**
   - Professional but personal
   - Share insights and learnings
   - Ask questions to drive engagement
   - Use "I" and share experiences
   
   **Structure:**
   ```
   [Hook - 1 compelling line]
   
   [Empty line]
   
   [Context - why this matters]
   
   [Empty line]
   
   [Main insight - 2-3 short paragraphs]
   
   [Empty line]
   
   [Call to action or question]
   
   #hashtag1 #hashtag2 #hashtag3
   ```
   
   ### Twitter/X
   
   **Format:**
   - 280 character limit per tweet
   - Threads for longer content (use 1/🧵 format)
   - No more than 2 hashtags per tweet
   
   **Thread Structure:**
   ```
   1/🧵 [Hook - the main insight]
   
   2/ [Supporting point 1]
   
   3/ [Supporting point 2]
   
   4/ [Example or evidence]
   
   5/ [Conclusion + CTA]
   ```
   
   ## Image Generation
   
   Every social media post needs an eye-catching image. Use the `generate_social_image` tool:
   
   ```
   generate_social_image(prompt="A detailed description...", platform="linkedin", slug="your-post-slug")
   ```
   
   The tool saves the image to `<platform>/<slug>/image.png`.
   
   ### Social Image Best Practices
   
   Social images need to work at small sizes in crowded feeds:
   - **Bold, simple compositions** - one clear focal point
   - **High contrast** - stands out when scrolling
   - **No text in image** - too small to read, platforms add their own
   - **Square or 4:5 ratio** - works across platforms
   
   ### Writing Effective Prompts
   
   Include these elements:
   
   1. **Single focal point**: One clear subject, not a busy scene
   2. **Bold style**: Vibrant colors, strong shapes, high contrast
   3. **Simple background**: Solid color, gradient, or subtle texture
   4. **Mood/energy**: Match the post tone (inspiring, urgent, thoughtful)
   
   ### Example Prompts
   
   **For an insight/tip post:**
   ```
   Single glowing lightbulb floating against a deep purple gradient background, lightbulb made of interconnected golden geometric lines, rays of soft light emanating outward. Minimal, striking, high contrast. Square composition.
   ```
   
   **For announcements/news:**
   ```
   Abstract rocket ship made of colorful geometric shapes launching upward with a trail of particles. Bright coral and teal color scheme against clean white background. Energetic, celebratory mood. Bold flat illustration style.
   ```
   
   **For thought-provoking content:**
   ```
   Two overlapping translucent circles, one blue one orange, creating a glowing intersection in the center. Represents collaboration or intersection of ideas. Dark charcoal background, soft ethereal glow. Minimalist and contemplative.
   ```
   
   ## Content Types
   
   ### Announcement Posts
   - Lead with the news
   - Explain the impact
   - Include link or next step
   
   ### Insight Posts
   - Share one specific learning
   - Explain the context briefly
   - Make it actionable
   
   ### Question Posts
   - Ask a genuine question
   - Provide your take first
   - Keep it focused on one topic
   
   ## Quality Checklist
   
   Before finishing:
   - [ ] Post saved to `linkedin/<slug>/post.md` or `tweets/<slug>/thread.md`
   - [ ] Image generated alongside the post
   - [ ] First line hooks attention
   - [ ] Content fits platform limits
   - [ ] Tone matches platform norms
   - [ ] Has clear CTA or question
   - [ ] Hashtags are relevant (not generic)
   

   They instruct the agent to call the researcher subagent first, write markdown under blogs/, linkedin/, or tweets/, and call generate_cover or generate_social_image for images.

   When you later create the agent and specify the skills folder(s), then the frontmatter of the SKILLS.md files from those skill folders get loaded this into the system prompt so the agent can use the skill when a task task matches a skill description.

Build the script

Create content_writer.ts in the project root. The following sections belong in one file, in order.

1. Add tools

   The researcher uses Tavily search. Blog and social workflows use the Google Generative AI SDK for image generation.

   import { tool } from "@langchain/core/tools";
   import * as z from "zod";
   import * as fs from "node:fs";
   import * as path from "node:path";
   
   const EXAMPLE_DIR = path.dirname(new URL(import.meta.url).pathname);
   
   const webSearch = tool(
     async ({ query, maxResults = 5, topic = "general" }) => {
       const apiKey = process.env.TAVILY_API_KEY;
       if (!apiKey) return { error: "TAVILY_API_KEY not set" };
       try {
         const { TavilyClient } = await import("tavily");
         const client = new TavilyClient({ apiKey });
         return client.search(query, { maxResults, topic });
       } catch (e) {
         return { error: `Search failed: ${e}` };
       }
     },
     {
       name: "web_search",
       description: "Search the web for current information.",
       schema: z.object({
         query: z.string().describe("The search query (be specific and detailed)"),
         maxResults: z
           .number()
           .optional()
           .describe("Number of results to return (default: 5)"),
         topic: z
           .enum(["general", "news"])
           .optional()
           .describe('"general" for most queries, "news" for current events'),
       }),
     },
   );
   
   const generateCover = tool(
     async ({ prompt, slug }) => {
       try {
         const { GoogleGenerativeAI } = await import("@google/generative-ai");
         const genai = new GoogleGenerativeAI(process.env.GOOGLE_API_KEY ?? "");
         const model = genai.getGenerativeModel({
           model: "gemini-2.5-flash-image",
         });
         const result = await model.generateContent(prompt);
         const part = result.response.candidates?.[0]?.content?.parts?.find(
           (p) => p.inlineData,
         );
         if (!part?.inlineData) return "No image generated";
         const outputPath = path.join(EXAMPLE_DIR, "blogs", slug, "hero.png");
         fs.mkdirSync(path.dirname(outputPath), { recursive: true });
         fs.writeFileSync(outputPath, Buffer.from(part.inlineData.data, "base64"));
         return `Image saved to ${outputPath}`;
       } catch (e) {
         return `Error: ${e}`;
       }
     },
     {
       name: "generate_cover",
       description: "Generate a cover image for a blog post.",
       schema: z.object({
         prompt: z
           .string()
           .describe("Detailed description of the image to generate."),
         slug: z
           .string()
           .describe("Blog post slug. Image saves to blogs/<slug>/hero.png"),
       }),
     },
   );
   
   const generateSocialImage = tool(
     async ({ prompt, platform, slug }) => {
       try {
         const { GoogleGenerativeAI } = await import("@google/generative-ai");
         const genai = new GoogleGenerativeAI(process.env.GOOGLE_API_KEY ?? "");
         const model = genai.getGenerativeModel({
           model: "gemini-2.5-flash-image",
         });
         const result = await model.generateContent(prompt);
         const part = result.response.candidates?.[0]?.content?.parts?.find(
           (p) => p.inlineData,
         );
         if (!part?.inlineData) return "No image generated";
         const outputPath = path.join(EXAMPLE_DIR, platform, slug, "image.png");
         fs.mkdirSync(path.dirname(outputPath), { recursive: true });
         fs.writeFileSync(outputPath, Buffer.from(part.inlineData.data, "base64"));
         return `Image saved to ${outputPath}`;
       } catch (e) {
         return `Error: ${e}`;
       }
     },
     {
       name: "generate_social_image",
       description: "Generate an image for a social media post.",
       schema: z.object({
         prompt: z
           .string()
           .describe("Detailed description of the image to generate."),
         platform: z.string().describe('Either "linkedin" or "tweets"'),
         slug: z
           .string()
           .describe("Post slug. Image saves to <platform>/<slug>/image.png"),
       }),
     },
   );
   
2. Create the agent

   When creating the deep agent with createDeepAgent, pass memory paths, the skills directory, image tools, an inline subagent definition, and a FilesystemBackend rooted at the example directory so paths like ./AGENTS.md and ./skills/ resolve correctly.

   Google

   import { createDeepAgent, FilesystemBackend } from "deepagents";
   
   function createContentWriter() {
     const researcherSubagent = {
       name: "researcher",
       description:
         "Research subagent with web search capability. Delegate research tasks here.",
       systemPrompt:
         "You are a research assistant. Use the web_search tool to find current, accurate information and return well-organized findings.",
       tools: [webSearch],
     };
   
     return createDeepAgent({
       model: "google-genai:gemini-3.5-flash",
       memory: ["./AGENTS.md"],
       skills: ["./skills/"],
       tools: [generateCover, generateSocialImage],
       subagents: [researcherSubagent],
       backend: new FilesystemBackend({ rootDir: EXAMPLE_DIR }),
     });
   }
   

   import { createDeepAgent, FilesystemBackend } from "deepagents";
   
   function createContentWriter() {
     const researcherSubagent = {
       name: "researcher",
       description:
         "Research subagent with web search capability. Delegate research tasks here.",
       systemPrompt:
         "You are a research assistant. Use the web_search tool to find current, accurate information and return well-organized findings.",
       tools: [webSearch],
     };
   
     return createDeepAgent({
       model: "openai:gpt-5.5",
       memory: ["./AGENTS.md"],
       skills: ["./skills/"],
       tools: [generateCover, generateSocialImage],
       subagents: [researcherSubagent],
       backend: new FilesystemBackend({ rootDir: EXAMPLE_DIR }),
     });
   }
   

   import { createDeepAgent, FilesystemBackend } from "deepagents";
   
   function createContentWriter() {
     const researcherSubagent = {
       name: "researcher",
       description:
         "Research subagent with web search capability. Delegate research tasks here.",
       systemPrompt:
         "You are a research assistant. Use the web_search tool to find current, accurate information and return well-organized findings.",
       tools: [webSearch],
     };
   
     return createDeepAgent({
       model: "anthropic:claude-sonnet-4-6",
       memory: ["./AGENTS.md"],
       skills: ["./skills/"],
       tools: [generateCover, generateSocialImage],
       subagents: [researcherSubagent],
       backend: new FilesystemBackend({ rootDir: EXAMPLE_DIR }),
     });
   }
   

   import { createDeepAgent, FilesystemBackend } from "deepagents";
   
   function createContentWriter() {
     const researcherSubagent = {
       name: "researcher",
       description:
         "Research subagent with web search capability. Delegate research tasks here.",
       systemPrompt:
         "You are a research assistant. Use the web_search tool to find current, accurate information and return well-organized findings.",
       tools: [webSearch],
     };
   
     return createDeepAgent({
       model: "openrouter:openrouter:z-ai/glm-5.2",
       memory: ["./AGENTS.md"],
       skills: ["./skills/"],
       tools: [generateCover, generateSocialImage],
       subagents: [researcherSubagent],
       backend: new FilesystemBackend({ rootDir: EXAMPLE_DIR }),
     });
   }
   

   import { createDeepAgent, FilesystemBackend } from "deepagents";
   
   function createContentWriter() {
     const researcherSubagent = {
       name: "researcher",
       description:
         "Research subagent with web search capability. Delegate research tasks here.",
       systemPrompt:
         "You are a research assistant. Use the web_search tool to find current, accurate information and return well-organized findings.",
       tools: [webSearch],
     };
   
     return createDeepAgent({
       model: "fireworks:accounts/fireworks/models/glm-5p2",
       memory: ["./AGENTS.md"],
       skills: ["./skills/"],
       tools: [generateCover, generateSocialImage],
       subagents: [researcherSubagent],
       backend: new FilesystemBackend({ rootDir: EXAMPLE_DIR }),
     });
   }
   

   import { createDeepAgent, FilesystemBackend } from "deepagents";
   
   function createContentWriter() {
     const researcherSubagent = {
       name: "researcher",
       description:
         "Research subagent with web search capability. Delegate research tasks here.",
       systemPrompt:
         "You are a research assistant. Use the web_search tool to find current, accurate information and return well-organized findings.",
       tools: [webSearch],
     };
   
     return createDeepAgent({
       model: "baseten:zai-org/GLM-5.2",
       memory: ["./AGENTS.md"],
       skills: ["./skills/"],
       tools: [generateCover, generateSocialImage],
       subagents: [researcherSubagent],
       backend: new FilesystemBackend({ rootDir: EXAMPLE_DIR }),
     });
   }
   

   import { createDeepAgent, FilesystemBackend } from "deepagents";
   
   function createContentWriter() {
     const researcherSubagent = {
       name: "researcher",
       description:
         "Research subagent with web search capability. Delegate research tasks here.",
       systemPrompt:
         "You are a research assistant. Use the web_search tool to find current, accurate information and return well-organized findings.",
       tools: [webSearch],
     };
   
     return createDeepAgent({
       model: "ollama:north-mini-code-1.0",
       memory: ["./AGENTS.md"],
       skills: ["./skills/"],
       tools: [generateCover, generateSocialImage],
       subagents: [researcherSubagent],
       backend: new FilesystemBackend({ rootDir: EXAMPLE_DIR }),
     });
   }
   
3. Add an entry point

   const task =
     process.argv.slice(2).join(" ") ||
     "Write a blog post about how AI agents are transforming software development";
   
   const agent = createContentWriter();
   const result = await agent.invoke({
     messages: [{ role: "user", content: task }],
     config: { configurable: { threadId: "content-builder-demo" } },
   });
   
   const messages = result.messages ?? [];
   for (const msg of messages) {
     if (msg.content) console.log(msg.content);
   }
   

Run the agent

The filesystem backend can read, write, and delete files under root_dir. Run only in a dedicated directory and review generated content before publishing.

From the project directory:

npx tsx content_writer.ts

Pass a prompt as extra arguments:

npx tsx content_writer.ts Write a blog post about prompt engineering

With LANGSMITH_API_KEY set, you can inspect runs in LangSmith.

Output

On success, the agent writes artifacts under the project root (the example directory), for example:

blogs/
└── prompt-engineering/
    ├── post.md
    └── hero.png
research/
└── prompt-engineering.md

Paths follow the skill instructions in SKILL.md.

Full code

Browse the complete content-builder-agent example on GitHub, including the Rich-based streaming UI.

Next steps

• Edit AGENTS.md to change brand voice and research requirements
• Add skills under skills/<name>/SKILL.md for new content types
• Add subagents in subagents.yaml and register tools in load_subagents
• Read Subagents, Skills, and Customization for deeper configuration

---

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