Locus product guide · Updated November 10, 2026

Exa MCP server: tools, free limits, setup and billing

Exa's official MCP server runs at https://mcp.exa.ai/mcp. It gives an agent web_search_exa and web_fetch_exa by default, plus web_search_advanced_exa and agent_run if you turn them on. It works with no API key at a free rate limit. With a key, calls bill at Exa API rates from a prepaid balance: searches by mode, and contents by the page. Exa adds $10 of free credit each month.

Setup, step by step

Step 1
Install the Exa plugin in Claude Code
The plugin adds the hosted MCP server and Exa skills. You can also type /plugin in Claude Code and search for Exa.
```
claude plugin install exa@claude-plugins-official
```
Step 2
Or add only the MCP server
Use this if you manage MCP servers by hand. No key is needed for light use.
```
claude mcp add --transport http exa https://mcp.exa.ai/mcp
```

Step 3

Add it to Codex

Codex takes the same URL.

codex mcp add exa --url https://mcp.exa.ai/mcp

Step 4
Add your API key when you hit the free limit
A 429 error means you reached the free rate limit. Send your key in the x-api-key header. The tools parameter turns on the opt-in tools.
```
{
  "exa": {
    "url": "https://mcp.exa.ai/mcp?tools=web_search_exa,web_fetch_exa,agent_run,web_search_advanced_exa",
    "headers": { "x-api-key": "YOUR_EXA_API_KEY" }
  }
}
```

What tools does the Exa MCP server have?

Two tools are on by default. Two more are opt-in through the tools parameter on the URL.

agent_run waits up to about 750 seconds. A longer run returns its ID, and you call agent_run again with runId to keep waiting.
Exa says web_search_exa suits everyday lookups. Turn on the advanced tool only when you need filters, because each extra tool adds to the context.

What tools does the Exa MCP server have?
Tool	Enabled	What it does
web_search_exa	By default	Searches the web and returns clean page content
web_fetch_exa	By default	Reads one or more URLs as markdown
web_search_advanced_exa	Opt-in	Full Search API: categories, domains, date ranges, highlights, summaries and subpages
agent_run	Opt-in, needs sign-in or a key	Runs Exa Agent for multi-step research and structured output

Do you need an Exa API key?

Not for casual use. The hosted server works keyless at a free rate limit and returns a 429 error once you pass it. Exa does not publish the keyless numbers on its MCP page.

Add a key, or sign in with OAuth, for production use and for agent_run. Keyed calls draw on your Exa balance at normal API rates.

How does Exa bill after the free tier?

Exa is pay as you go from a prepaid balance. Each kind of call has its own rate. Checked November 10, 2026.

Free credit: $10 a month that resets and does not build up, plus a one-time $10 bonus.
Rate limits: 10 searches a second, 5 for Deep, 100 for contents. Buying $1,000 in 30 days raises search to 25 a second for 90 days.
When the balance runs out, calls fail with a 402 error.

How does Exa bill after the free tier?
Item	How Exa bills it
Search, Lite mode	Per search, up to 10 results, at the lowest search rate
Search, Auto mode	Per search, up to 10 results, at a rate between Lite and Deep
Search, Deep mode	Per search, up to 10 results, at the highest search rate
Contents	Per page returned
Answer	Per request
Agent	By usage, per run

Exa pricing in detail

How do you call Exa through Locus Pro?

Locus Pro reaches Exa through one MCP connection and one credit balance, with no Exa account. 1,000 credits cost $1. Catalog search and describe are free, and max_credits caps any call.

Exa on Locus is a seller listing on x402. Locus has not reviewed it and cannot promise it stays available. Prices are live catalog prices on November 10, 2026.

MCP URL: https://api.paywithlocus.com/api/credits/mcp
Or tell your agent: Install Locus Pro by following https://paywithlocus.com/SKILL.md

How do you call Exa through Locus Pro?
Locus endpoint	Provider review	Price per call
exa/search	Seller listing, not reviewed	From 8.5 credits ($0.0085), priced live
exa/contents	Seller listing, not reviewed	From 1.2 credits ($0.0012)
perplexity/search	Known vendor	5.8 credits ($0.0058), fixed
firecrawl/search	Known vendor	1.7 credits ($0.0017), fixed
router/web-search	Locus router over several engines	1 to 10.1 credits

Should you use Exa's MCP server or Locus Pro?

Use Exa's server if Exa is your only search provider. It needs no key for light use, and it has Exa Agent and the advanced search filters. Exa calls can also cost less with your own Exa account and API key.

Use Locus Pro when one agent needs Exa next to Perplexity, Firecrawl, Brave or non-search APIs, and you want one connection, one balance and a price ceiling per call.

Frequently asked questions

Does the Exa MCP server work without an API key?

Yes. The hosted server at mcp.exa.ai works keyless for search and fetch at a free rate limit. Agent runs need a sign-in or a key.

How do I turn on Exa advanced search in MCP?

Add a tools parameter to the server URL that lists web_search_advanced_exa, plus any default tools you want to keep. Then restart your MCP client.

What happens when my Exa balance runs out?

Keyed calls fail with a 402 error until you add credit. The free $10 a month resets on its own, but unused free credit does not carry over.

Can I call Exa without an Exa account?

Yes, through Locus Pro. Exa search and contents are a seller listing on x402 that Locus has not reviewed, paid per call from prepaid credits. For Exa Agent, use Exa's own server.

Implementation references

Use these first-party references for current request contracts and account requirements. Tool availability, prices, and negotiated terms can change.

Sources

Third-party details were checked on November 10, 2026. Vendors change pricing and features often, so confirm on their site before you decide.