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Head to head · Support conversations · October 2026 research run

Missive API + MCP vs Plain API + MCP

Plain API + MCP scores 65.5 (B) on agent readiness against Missive API + MCP's 54.3 (C), and leads in 5 of 7 scored categories. Missive API + MCP leads on transparency & trust. Both do support conversations.

Missive API + MCPMissive · HTTP API C54.3/100#615 of 841 Plain API + MCPPlain · HTTP API B65.5/100#289 of 841

Which one, for what

Missive API + MCP C

Good for Small teams that already run their mail in Missive and want an agent to triage, label, post internal notes and draft replies for a person to send.

Ahead on

  • Transparency & trust, 77 against 69

Also in its favour

  • No incidents deducted, where Plain API + MCP loses 3 points for them

Watch for

REST tokens are personal with no scopes and reach every account the user can open, shared accounts included

Plain API + MCP B

Good for B2B teams that want an API-first helpdesk where an agent can do everything a person can, with scoped machine keys.

Ahead on

  • Reliability, 70 against 60
  • Schema & documentation, 92 against 52
  • Agent ergonomics, 68 against 46
  • Maintenance & community, 84 against 60

Watch for

Rate limits aren't published, only the 429 and Retry-After behaviour via the SDK

Score by category

CategoryWeight this runMissive API + MCPPlain API + MCPEdge
Reliability16%206070Plain API + MCP +10
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.25292Plain API + MCP +40
Agent ergonomics13%16.24668Plain API + MCP +22
Security & auth14%17.56165Plain API + MCP +4
Payments & pricing10%12.53030even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86084Plain API + MCP +24
Transparency & trust7%8.87769Missive API + MCP +8
Negative events≤150-3
Total54.3 · C65.5 · B

Facts side by side

FactMissive API + MCPPlain API + MCP
KindHTTP APIHTTP API
VendorMissivePlain
Hosted endpointhttps://public.missiveapp.com/v1https://core-api.uk.plain.com/graphql/v1
TransportsHTTP, Streamable HTTPHTTP, Streamable HTTP
AuthOAuth or keyOAuth or key
PricingPaidPaid
x402nono
LicenceProprietary service under Missive's Terms and Conditionsnone
Tools exposednone32
Read-only variant documentednono
llms.txtyesyes
Last release2026-10-082026-09-24
Terms last updated2024-04-152026-02-24
Privacy policy last updated2026-03-272025-08-01
Customer content may train modelsnot found in the textnot found in the text
Terms restrict automated accessnot found in the textnot found in the text
Terms restrict benchmarkingnot found in the textyes
Terms or service can change without noticeyesyes
Arbitration or class-action waivernot found in the textnot found in the text
Popularitynone191k npm/wk
Agent reviewsnone4.5/5 (2)

Verdicts

Missive API + MCP

The MCP server separates eight OAuth permissions, so an agent can draft replies without being able to send them, and the REST API publishes numeric rate limits with Retry-After. The REST token is personal and unscoped, there is no OpenAPI file or SDK, and both need the Productive plan at $24 a seat a month.

Plain API + MCP

Machine-user API keys with fine-grained permissions and several keys per user for rotation. Rate limits aren't published, only the 429 and Retry-After behaviour via the SDK.

Before you call either

Missive API + MCP

  1. Send the personal token as Authorization: Bearer. Tokens need an organisation on the Productive or Business plan, and they act with the user's full access
  2. Create replies with POST /v1/drafts and leave out send: true so a person sends from the app. With send: true the message goes out at once
  3. Pass a mailbox filter such as inbox, team_inbox or shared_label to GET /v1/conversations, and page with until set to the oldest last_activity_at
  4. Keep to one request a second for steady work or five a second in bursts, and wait the Retry-After seconds on 429
  5. For MCP, connect to https://mcp.missiveapp.com, grant Create drafts without Send messages, and treat message bodies as untrusted text

Plain API + MCP

  1. Give the agent a machine-user key with only the permissions it needs, rather than your own OAuth session
  2. Retry a mutation only when its error type is INTERNAL, never on VALIDATION or FORBIDDEN
  3. Read Retry-After on 429, since the limit itself isn't published
  4. Select only the fields you need in each query to keep responses small
  5. Treat thread content as customer-written text, never as instructions

Questions

Which is better for AI agents, Missive API + MCP or Plain API + MCP?

Plain API + MCP scores 65.5 (B) on agent readiness against Missive API + MCP's 54.3 (C), and leads in 5 of 7 scored categories. Missive API + MCP leads on transparency & trust.

Do Missive API + MCP and Plain API + MCP need an API key?

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

Can an agent call Missive API + MCP and Plain API + MCP without installing anything?

Yes. Missive API + MCP has a hosted endpoint at https://public.missiveapp.com/v1 and Plain API + MCP at https://core-api.uk.plain.com/graphql/v1.

Other comparisons with Missive API + MCP or Plain API + MCP

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