MCP is easy until you have a dozen servers
If you have been following this series, you have already seen how MCP servers work. A post about Cursor AI and MCP walked through building one from scratch, and the publishing pipeline post used MCP connections to Google Drive and Gmail.
The trouble with that approach is not MCP. It is MCP sprawl. Each new tool means another server to install, another OAuth flow, another set of credentials to rotate and another block in mcp.json. With five integrations it is manageable. With twenty it becomes a second job, and a rather dull one.
Composio sits between the agent and those services. It handles authentication and tool access, and its Tool Router lets the agent discover only the tools it needs instead of loading a giant catalogue into its context. That second part is the interesting one.
A quick word on vocabulary, because the names get tangled:
- Composio is the integration platform.
- Sessions (Tool Router) are the mechanism that gives an agent scoped, dynamically discoverable access to Composio’s tools.
- MCP is the protocol that exposes a session to compatible clients such as Claude, Cursor or Claude Code.
- Rube was an earlier Composio product built on the same idea. You will still meet the name in older tutorials.
This post covers how Tool Router works, what it costs, how to set it up in about fifteen minutes, and when it is, and is not, worth the extra dependency.
What problem does Composio solve?
Without Composio, connecting Claude to GitHub, Notion and Gmail means three MCP servers, three OAuth apps, three sets of tokens and three configuration blocks. When one of them breaks (a token expires, an API version changes, a scope needs updating) you fix it yourself.
With Composio, you connect each service once. Your agent connects to a single Composio MCP endpoint, and Composio routes requests to the right service and manages the connected account and token lifecycle for you. You normally do not have to handle refresh tokens yourself, although a revoked permission or a changed scope will still need your attention.
Security deserves a precise sentence here. Composio publishes its certifications and policies at its trust centre. Zero data retention is not the default: according to the pricing page it is an optional add-on (not included on the free Hobby plan, an extra $0.0001 per tool call on Pro, and included on Enterprise). Check the current terms before connecting anything sensitive.
How does Tool Router solve tool discovery and context bloat?
Tool definitions consume context window tokens. Each tool needs a name, a description and a parameter schema, which in my experience costs several hundred tokens per tool. A modest setup with 15 tools can use thousands of tokens before the conversation even starts.
Composio’s answer is Tool Router, which went generally available in the Python and TypeScript SDKs in December 2025. Each user gets a scoped session that starts with a small set of meta-tools: search for tools, manage connections, execute a tool, and a sandbox for large responses. The agent asks “what can I use to send an email?” and gets back the Gmail tools it needs, right then, without carrying tool definitions for Linear, Figma or Salesforce.
Tool Router does not eliminate tool definitions. It makes them discoverable on demand. The agent starts small, searches, and loads only the schemas the task requires. (Composio’s docs also warn that preloading tools adds to the context window, so preload sparingly.)
Think of arriving at a library and being handed every book at once versus being able to search the catalogue. The catalogue approach scales; the “every book at once” approach does not.
Composio pricing: free tier limits and overage costs
Composio changed its pricing on 15 August 2026, so it is worth being precise. As of 7 October 2026, the tiers on composio.dev/pricing are:
| Tier |
Price |
Included |
| Hobby (the free tier) |
$0 |
100,000 tool calls/month, 50,000 trigger events/month, 3 team members; usage pauses at the cap |
| Pro |
$29/month |
Everything in Hobby, a $29 monthly usage credit, unlimited team members, spend controls and add-ons; $0.0003 per tool call beyond the included volume |
| Enterprise |
Custom |
Committed volume and discounts, custom billing terms, zero data retention included |
A few “premium tools” that use Composio-hosted credentials for paid third-party providers (web search or browser automation, for example) are billed separately. Existing customers stay on their current plan through 31 December 2026, so check your dashboard to see which pricing applies to you.
The free tier is generous for personal use. A blog workflow that publishes four posts per month, each touching GitHub, Google Drive and Gmail, might use a few hundred tool calls in total. The catalogue is described on the pricing page as 1,500+ toolkits, which is the number I use throughout this post.
The pricing table will go stale. Composio has revised these numbers at least once in 2026, and the third-party reviews I checked disagree with each other. Treat the table as a snapshot and confirm the current terms before you budget around it.
How to set up Composio with Claude, Cursor and the Python SDK in fifteen minutes
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Using Composio with Claude and ChatGPT: what works today
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Composio examples: GitHub, Slack, Notion and Gmail automation with Claude
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Composio in my multi-agent publishing pipeline
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Composio limitations: costs, context window and security
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Is Composio worth using?
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References
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