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Head to head · Spend transactions · October 2026 research run

Mercury API vs Pleo API + MCP

Mercury API and Pleo API + MCP score within a point of each other on agent readiness, 63.8 (B) and 62.9 (B). Pleo API + MCP leads on reliability, schema & documentation and transparency & trust. Both do spend transactions.

Mercury APIMercury Technologies, Inc. · HTTP API B63.8/100#293 of 722 Pleo API + MCPPleo Technologies A/S · HTTP API B62.9/100#325 of 722

Which one, for what

Mercury API B

Good for A company that banks with Mercury and wants an agent to read balances and transactions, set notes and categories, upload receipts, issue virtual cards with spend limits and queue payments for human approval.

Ahead on

  • Agent ergonomics, 68 against 55
  • Security & auth, 82 against 71
  • Payments & pricing, 30 against 15

Watch for

No rate limits with numbers and no 429 handling were found in the reviewed documentation

Pleo API + MCP B

Good for An agent that completes, codes, reviews and queues expenses for a Pleo customer on the Optimise plan, or for a bookkeeping integration that exports accounting entries and syncs tags, tax codes, accounts and vendors.

Ahead on

  • Reliability, 71 against 59
  • Schema & documentation, 82 against 72
  • Transparency & trust, 75 against 63

Watch for

The pricing page lists MCP on the Optimise plan only (£18 per user per month, three users minimum, sold through a demo)

Score by category

CategoryWeight this runMercury APIPleo API + MCPEdge
Reliability16%205971Pleo API + MCP +12
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27282Pleo API + MCP +10
Agent ergonomics13%16.26855Mercury API +13
Security & auth14%17.58271Mercury API +11
Payments & pricing10%12.53015Mercury API +15
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86464even
Transparency & trust7%8.86375Pleo API + MCP +12
Negative events≤1500
Total63.8 · B62.9 · B

Facts side by side

FactMercury APIPleo API + MCP
KindHTTP APIHTTP API
VendorMercury Technologies, Inc.Pleo Technologies A/S
Hosted endpointhttps://api.mercury.com/api/v1https://external.pleo.io
TransportsHTTPHTTP, Streamable HTTP
AuthOAuth or keyOAuth or key
PricingFreemiumPaid
x402nono
LicenceProprietary service under Mercury's Terms of Use. The Mercury CLI on GitHub is Apache-2.0Proprietary service under Pleo's Master Service Agreement, API Terms of Service and AI Access Terms
Tools exposed35none
Read-only variant documentedyesno
llms.txtyesyes
Last release2026-08-122026-10-02
Terms last updatedno date givenno date given
Privacy policy last updatedno date given
Customer content may train modelsnot found in the textnot found in the text
Terms restrict automated accessyesnot found in the text
Terms restrict benchmarkingyesnot found in the text
Terms or service can change without noticenot found in the textnot found in the text
Arbitration or class-action waiveryesnot found in the text

Verdicts

Mercury API

Custom tokens take per-endpoint scopes, write tokens need an IP allowlist, and payments can be queued for approval in the dashboard through POST /account/{accountId}/request-send-money. No rate limits, error catalogue or SLA were found in the reviewed documentation, the changelog carries no dates, and the MCP server is beta.

Pleo API + MCP

The hosted MCP server acts with the connecting user's own Pleo permissions, is off until an admin enables it per entity, and can't move money, change cards or alter limits. It is listed only on the Optimise plan, its tool definitions aren't published, API keys need enabling by Pleo support, and no official SDK or SLA was found.

Before you call either

Mercury API

  1. Ask for a Custom token with only the scopes the task needs. Scopes can't be edited later, and a token unused for 45 days is deleted.
  2. Without a fixed IP address, send payments through POST /account/{accountId}/request-send-money. Direct sends through POST /account/{accountId}/transactions need an allowlisted IP.
  3. Send a stored idempotencyKey with every payment. The same recipient, account, amount and method within 24 hours returns 400 even with a new key.
  4. Set limit on list calls. GET /transactions returns up to 1,000 rows by default.
  5. Test against https://api-sandbox.mercury.com/api/v1/ with a sandbox token. Webhooks aren't available in the sandbox.

Pleo API + MCP

  1. Ask a company admin to enable Pleo MCP access under Settings, General, Pleo AI for each entity before connecting. It is off by default
  2. Name the entity in every request when working outside the default one. Each MCP request targets one entity and the choice doesn't persist
  3. Set the AI client to require approval for Pleo write tools. Pleo leaves confirmation to the client and doesn't enforce it server-side
  4. Send API keys as the Basic auth username with an empty password to external.pleo.io. Legacy tokens for openapi.pleo.io don't work there
  5. Budget every endpoint against one bucket of 600 requests a minute per credential, and on 429 wait for Retry-After or back off from one second
  6. Swap mcp.staging.pleo.io for mcp.pleo.io in the Claude Code command when moving from staging to production. Each needs its own OAuth sign-in

Questions

Which is better for AI agents, Mercury API or Pleo API + MCP?

Mercury API and Pleo API + MCP score within a point of each other on agent readiness, 63.8 (B) and 62.9 (B). Pleo API + MCP leads on reliability, schema & documentation and transparency & trust.

Do Mercury API and Pleo API + MCP need an API key?

Both take an API key or an OAuth sign-in.

Can an agent call Mercury API and Pleo API + MCP without installing anything?

Yes. Mercury API has a hosted endpoint at https://api.mercury.com/api/v1 and Pleo API + MCP at https://external.pleo.io.

Other comparisons with Mercury API or Pleo API + MCP

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