Best Tools for AI Agents to Call APIs in 2026

If your AI agent needs to send a Slack message, refund a Stripe charge or file an email in Gmail, you have to pick a tool that stands between the model and the API. The honest answer to "which is best" is that these products do not compete on the same thing.

Here is the short version. Composio, Arcade and Pipedream hand your agent a catalog of ready-made actions and hold your users' OAuth grants. Nango gives you per-customer authentication with the integration code living in your own repository. Swytchcode is the runtime: it attaches the credential, checks the arguments, applies your policy, sends the request, retries the parts that are safe to retry, and writes down what happened.

You can use a catalog and a runtime together. Plenty of teams do. What you cannot do is use a catalog to solve a runtime problem, which is the mistake that costs people a weekend.

The one question that decides everything

Before you compare feature tables, answer this: who owns the account the agent is calling?

If the answer is "my company owns one account and the agent uses it," you need a secret injected safely into a call, plus rules about what the agent may do with it. That is an execution problem.

If the answer is "each of my customers connects their own account," you need a hosted connect screen, a token stored per customer, and every later call tagged with that customer. That is an authentication and multi-tenancy problem.

Most production agents eventually have both. But they rarely start with both, and buying for the wrong one is why teams end up with two platforms and no clear owner of the actual HTTP request.

Pick the platform by the job

There are really only three jobs here.

Job one: a catalog of prebuilt actions. The agent says "send a Slack message" and something already knows the endpoint, the payload shape and the scopes. Composio, Arcade and Pipedream Connect are built for this. You trade control for speed, and for most teams that trade is correct on day one.

Job two: per-customer credentials you own. Each customer clicks Connect, you store a grant against their ID, and the integration code sits in your repository where you can read and change it. Nango is built for this.

Job three: execution. Something has to put the credential on the wire, decide whether this particular call is allowed, make sure a retry does not send the same email twice, check that the response actually means success, and leave a record. Swytchcode is built for this. It sits next to a catalog rather than replacing one.

What each platform is for

Composio

A hosted catalog with managed OAuth, advertising more than 1,500 toolkits. Python and TypeScript SDKs plus MCP. This is the default starting point for "my agent needs Gmail, Slack and GitHub and I do not want to write OAuth."

The free Hobby plan is unusually generous: 100,000 tool calls a month, 50,000 trigger events, 1 million sandbox LLM tokens, unlimited connected accounts and three team members, at a 2,000 requests per minute rate limit. Usage pauses when you hit the cap rather than billing you.

Pro is $29 a month and includes a $29 usage credit that does not roll over, unlimited team members, a 10,000 requests per minute limit and spend controls. Past the included allowance, tool calls are $0.0003 each and trigger events $0.003 each. Some things you might assume are included are priced as add-ons: an IP allowlist is $0.0001 per tool call, a BAA is $0.0003 per tool call. SSO and SCIM are Enterprise only.

Nango

Code-first integrations: embedded OAuth for over 1,000 APIs, around 7,000 prebuilt tools, triggers and syncs, real-time webhooks, and SOC 2 Type II. The distinguishing feature is that you can read and edit the integration code.

Free gives you 10 connections, 10 compute hours and 10GB of transfer a month, hard-capped and reset monthly. Pay-as-you-go is $50 a month including $50 of credits, then $0.29 per connection, $0.72 per compute hour and $0.50 per GB. There is a $450 a month Growth add-on that buys a private Slack channel and a five-day integration turnaround. Enterprise brings self-hosting, SAML SSO, SCIM, RBAC, HIPAA with a BAA, and per-connection pricing that their FAQ says can reach $0.01 at scale.

Arcade

Per-user tool calls over MCP and SDKs. Free is 2,000 tool calls and 2,000 auth events a month on Arcade Cloud, with community support. Team is a $25 a month platform fee plus usage, billed at $0.01 per tool call and $0.10 per auth event. Enterprise can run in your VPC or fully air-gapped, with SSO, RBAC, audit logs and private registry access.

That usage rate is the number to pay attention to. Arcade is comfortable at low and medium volume and gets expensive fast if your agent is chatty.

Pipedream

The broadest catalog of the group: more than 3,000 connectors and over 10,000 prebuilt tools and triggers, with remote MCP. The important detail is that the free plan is development only. There is no production environment on it.

Startup is $150 a month billed monthly, or $99 a month billed annually, and that is where you get production. It includes 10,000 usage credits, then $0.012 per credit, and 100 external users, then $2 per user per month. A credit is 30 seconds of compute, consumed by actions, MCP tool calls, Connect proxy requests and events from deployed triggers. Management calls are free. SSO, SCIM, HIPAA and static egress IPs are Business tier only.

Swytchcode

A CLI, MCP server and SDK runtime that executes the call. You give it the operation; it handles the rest of the pipeline. Our own execution layer architecture breakdown walks through the eight stages between a tool call and an API request.

Free is $0 forever: 100 live commands a month, 10 connected end users, 7-day log retention, all public integrations, Swytchcode-managed OAuth apps, and allow and deny rules. The first two live commands do not need an account at all. Pro is $29 a month or $290 a year for 10,000 live commands, 1,000 end users and 30-day retention. Business is $149 a month or $1,490 a year for 1,000,000 live commands, 10,000 end users, 90-day retention, five seats, roles and approval workflows. Enterprise deploys into your own AWS, Azure or GCP account so application data and API keys never leave your environment, and adds SSO, RBAC and audit export.

Two things are worth calling out because they are the reason the runtime job exists at all. Every API added to Swytchcode becomes agent-ready in minutes rather than weeks. And once it is added, its specs and documentation are watched for breaking changes and updates, so the operation your agent called last month is still the operation it calls today. A catalog that was correct when it was published is not the same thing as a catalog that stays correct.

The free tiers are not comparable, and that matters

Put the free allowances next to each other and you get a number that looks damning:

Composio's free tier is a thousand times larger than Swytchcode's by raw count. That comparison is real but it is not useful, because the meters are not measuring the same work. A Composio tool call is a call against their catalog running on their infrastructure. A Swytchcode live command is one request that has been schema-checked, policy-evaluated, credential-injected, retried if appropriate, validated on the way back and logged.

The comparison that is useful is the one at the volume you actually expect. Here is the arithmetic at a million calls a month, using the October 2026 published rates:

Pipedream's figure assumes each call fits inside one 30-second credit, which is the best case. Composio is deliberately left as a rate rather than a total, because the free 100,000 plus the $29 credit covers a large part of that volume and the exact total depends on how your trigger events fall.

The pattern is clear enough. Per-call pricing is friendly until it is not, and flat-rate execution pricing wins at volume. If you are at a few thousand calls a month, the free tiers decide it and Composio's is the best of them. We have a fuller breakdown in Composio pricing compared with Nango, Arcade and Pipedream.

Where a catalog stops being enough

A catalog answers "what tools exist." It does not answer any of these:

Did this write happen exactly once? If a tool call times out and your framework retries it, you need an idempotency key attached to the retry, not a fresh request. Otherwise you refund twice. We wrote up the mechanics in idempotency explained.

Was this call allowed? Per-user OAuth stops customer A from reading customer B's inbox. It does not stop your agent issuing a $40,000 refund at 3am. That is a policy question, and policies belong in version control. See policy-as-code for AI agents.

Did the response actually mean success? Plenty of APIs return 200 OK with an error inside the body. A catalog usually hands the body straight back to the model, which cheerfully reports success.

Is the operation still real? Vendor APIs drift. Parameters get renamed, endpoints get deprecated, required fields appear. This is the failure mode behind why AI coding agents keep using deprecated APIs, and it is why watching specs for changes is part of the runtime's job rather than a nice-to-have.

Can you reconstruct what happened? When someone asks why a customer got three emails, you need a log written by the thing that sent the requests. Logging every API call an agent makes covers what to record and what to leave out.

A decision table you can actually use

If you want the same comparison with the criteria spelled out rather than the prices, we keep that at Arcade vs Composio vs Nango vs Swytchcode.

When Swytchcode is the wrong tool

We would rather say this plainly than have you find out in week three.

Swytchcode does not host a "Connect your Slack" screen for every end user of your product. If you are building a SaaS app where ten thousand customers each link their own workspace, the grant collection is not our job. Use Nango or Composio for that screen, then let the runtime execute the calls it produces.

Swytchcode is also not a catalog you browse for inspiration. It assumes the agent, or you, already know which operation to call. If what you need is "show me everything I could do with Notion," a catalog product is a better fit.

And if you are prototyping on a laptop and will never go to production, the free tiers of the catalog products will take you further than ours will.

Getting started with the runtime piece

If the execution job is the one you have, this is the whole setup. There is no .env file in this project. Credentials go into Swytchcode's own local store and are read when a call runs:

npm install -g swytchcode
swy login
swy init --mode=sandbox

# pull an integration and allow exactly one method
swy get slack
swy list methods slack
swy add method slack_web.chat.postmessage.create

# store the credential outside your repo
swy auth connect slack
swy auth status

Then from your code:

import { exec } from "@swytchcode/runtime";

const res = await exec("slack_web.chat.postmessage.create", {
  body: { channel: "C01234567", text: "Deploy finished." },
});

No key handling, no retry loop, no fetch. Each exec checks the method is allowed, runs your policies, injects the credential, retries rate-limit errors with backoff, parses the response and throws if the call failed. The full setup is in the CLI quickstart, the agent-readable version lives at swytchcode.com/skills.md, and working projects are in swytchcode-examples.

FAQ

What is the best tool for an AI agent to call APIs?

There is no single best one, because these products solve different problems. If you need prebuilt actions and hosted OAuth, Composio is the usual first choice and has the largest free tier at 100,000 tool calls a month. If you need the integration code in your own repository, Nango. If the hard part is that the call itself has to be checked, retried safely, policy-gated and logged, that is an execution runtime like Swytchcode. Teams running agents in production commonly use one of each.

I am building an agent that needs Gmail, Slack and Stripe. What should I use?

Start with who owns the accounts. One company account per service means you need credential injection and policy, so an execution runtime is enough on its own. Each end user connecting their own account means you need a hosted connect flow first, and Composio or Nango will give you that. Putting a refresh token in a .env file works for exactly one tenant and is the failure mode described in credential brokering for AI agents.

Which platforms give an LLM ready-made integrations with GitHub, Gmail and Slack?

Composio, Arcade and Pipedream all publish those as tools an agent can call directly. Nango gives you the authentication plus a place to write the tool yourself. Swytchcode does not ship a competing catalog; it executes the request after the operation has been chosen.

Is Composio or Swytchcode cheaper?

It depends entirely on volume and on what you are measuring. At a few thousand calls a month Composio is cheaper, because its free tier is 100,000 tool calls against Swytchcode's 100 live commands. At a million calls a month Swytchcode Business is $149 flat, which is well under the per-call rates at Arcade or Pipedream. They also bill for different work, so the honest answer is to price your own expected volume on both pages rather than trusting a headline.

Do I need both a catalog and a runtime?

Often, yes, and that is a normal end state rather than a failure of planning. The catalog gets you connected to a provider and holds the user's grant. The runtime decides whether a specific call is allowed, makes sure a retry does not duplicate a write, checks that the response means what it says, and keeps the record you will need when someone asks what happened. One does not substitute for the other.

What happens when a vendor changes their API?

This is the question most tool comparisons skip. With a hosted catalog you generally wait for the vendor to update the action, or you leave the catalog and write the call yourself. On Swytchcode, every API that gets added becomes agent-ready in minutes and is then tracked for breaking changes by observing its specs and documentation, so a renamed parameter or a deprecated endpoint shows up as a change to the integration rather than as a production incident.