fastn vs Composio
A tool-calling layer for AI agents, with a large catalog of app integrations exposed as agent tools.
What Composio is good at
A genuinely large catalog. Their public directory lists over 1,000 toolkits, which is among the broadest available to agent builders.
Agent-native from the start, with SDKs and auth handling aimed squarely at people writing agents rather than at integration engineers.
Fast to a working prototype when you are the one building the agent and connecting your own accounts.
The actual difference
Composio is built for the team building an agent. fastn is built for the SaaS company whose CUSTOMERS need integrations. That shows up in the tenancy model: with an agent-tooling platform you generally hold the credentials and the agent acts as you, whereas an embedded platform gives every one of your customers their own authorised connection, isolated from the others, configured to their own fields and reachable from inside your product.
Choose Composio when
You are building an agent for your own team, you hold the credentials, and you want the broadest tool catalog with the least ceremony.
Choose fastn when
Your customers each need to connect their own accounts inside your product, and the same connections should also be available to your agents under per-tenant governance.
The question that settles it
Can your customers connect and configure their own accounts, inside your product, without you deploying anything?
Questions people actually ask
Is fastn a drop-in replacement for Composio?
Not exactly, because they solve different halves of the problem. If all you need is tools for an agent you operate, Composio does that directly. fastn covers that case too, but it exists mainly for the case Composio is not shaped for: your customers authorising their own accounts inside your product, with each tenant isolated.
How do the catalogs compare?
Both are large, and raw connector counts are a poor way to choose. What matters more is whether a connector supports the objects and writes you need for the specific customers you have, and who fixes it when the vendor changes an endpoint. Ask both for the depth on the three systems your customers actually run.
Other comparisons
The fastest way to judge this is to connect one system and see what your customer would see.
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