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Context Capsule

@Johnny-Z13

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About Context Capsule

Portable context for agent workflows — structured handoff packets for AI agents

#ai-agents#context#handoff#mcp#workflow#multi-agent#llm

Config

Add this server to your MCP-compatible client using the configuration below.

{
  "mcpServers": {
    "contextcapsule": {
      "command": "npx",
      "args": [
        "-y",
        "@contextcapsule/mcp-server"
      ],
      "env": {
        "CONTEXTCAPSULE_API_KEY": "ak_your_key_here"
      }
    }
  }
}

Tools

3

Create a Context Capsule to hand off execution context between agents or sessions. Include a summary of what happened, key decisions made, and what should happen next. Capsules are structured, compressed, ephemeral context packets. Returns a capsule_id and capsule_url. Capsules expire after 7 days by default.

Fetch a Context Capsule to resume work from where another agent left off. Returns the full capsule data: summary, decisions, next_steps, payload, and refs. Use this to pick up execution context from a previous session or agent. No API key required.

Get a free Context Capsule API key. Returns the key directly — save it immediately, it cannot be retrieved later. Only needed once. After signup, configure the key as CONTEXTCAPSULE_API_KEY environment variable to use create_capsule. Free tier: 500 capsules per month.

Overview

What is Context Capsule?

Context Capsule is a portable execution context for agent workflows. It packages structured, compressed, ephemeral context (facts, state, next-step intent) that travels between agents, sessions, and tools, so agents can resume where they left off instead of restarting.

How to use Context Capsule?

Get an API key via POST /v1/auth/signup, then create a capsule with POST /v1/capsules and fetch it with GET /v1/capsules/:id. Alternatively, use the MCP server by running npx -y @contextcapsule/mcp-server and configuring it in any MCP-compatible client (e.g., Claude Desktop) with your API key.

Key features of Context Capsule

  • Structured context packet with summary, decisions, next steps, payload, and refs.
  • Capsules auto-expire after 7 days (configurable via expires_in).
  • Idempotent creation with idempotency_key to prevent duplicates on retry.
  • MCP server provides create_capsule and fetch_capsule tools.
  • Rate-limited endpoints (60 create/min per key, 120 fetch/min per IP).
  • Self-hostable with Node.js 18+, PostgreSQL, and Vercel/Neon stack.

Use cases of Context Capsule

  • Handoff between two agents in a multi-agent workflow (e.g., schema migration to testing).
  • Resume a long-running task after a session interrupt.
  • Pass execution context between different tools or services in a pipeline.
  • Replace manual prompt summarization with a machine‑readable capsule.

FAQ from Context Capsule

What fields does a capsule contain?

A capsule always includes a summary (≤500 chars), and optionally decisions (up to 20 strings), next_steps (up to 20 strings), a payload (up to 32KB JSON), and refs (workflow/agent/session IDs).

How long does a capsule live?

By default 7 days. You can set expires_in to any value between 60 and 604800 seconds. Expired capsules are automatically cleaned up.

How do I authenticate?

Create an API key via POST /v1/auth/signup (save the returned key immediately). Use that key as a Bearer token in the Authorization header for create requests. Fetching capsules does not require auth.

Can I self-host Context Capsule?

Yes. Requirements: Node.js 18+, PostgreSQL. Clone the repo, copy .env.example, set DATABASE_URL and BASE_URL, run migrations, seed an API key, then start with npm run dev.

What are the rate limits?

Create capsule: 60 requests per minute per API key. Fetch capsule: 120 requests per minute per IP. Signup: 5 requests per minute per IP.

Frequently asked questions

What fields does a capsule contain?

A capsule always includes a `summary` (≤500 chars), and optionally `decisions` (up to 20 strings), `next_steps` (up to 20 strings), a `payload` (up to 32KB JSON), and `refs` (workflow/agent/session IDs).

How long does a capsule live?

By default 7 days. You can set `expires_in` to any value between 60 and 604800 seconds. Expired capsules are automatically cleaned up.

How do I authenticate?

Create an API key via `POST /v1/auth/signup` (save the returned key immediately). Use that key as a Bearer token in the `Authorization` header for create requests. Fetching capsules does not require auth.

Can I self-host Context Capsule?

Yes. Requirements: Node.js 18+, PostgreSQL. Clone the repo, copy `.env.example`, set `DATABASE_URL` and `BASE_URL`, run migrations, seed an API key, then start with `npm run dev`.

What are the rate limits?

Create capsule: 60 requests per minute per API key. Fetch capsule: 120 requests per minute per IP. Signup: 5 requests per minute per IP.

Comments

Basic information

Category

Other

License

MIT

Transports

stdio

Author

Johnny-Z13

Submitted by

Johnny Venables

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