Mattermost API
★ Only Publicly Available OpenAPI DocumentCommunicationsChat Messagingbearer8 EndpointsREST
For Agents
Authenticate users, fetch team and channel context, and post messages on a self-hosted Mattermost server with bearer-token auth.
Use for: Log in to Mattermost with username and password and store the session token, Get the currently authenticated Mattermost user via the `me` endpoint, List all teams the user is a member of, Post a message to a Mattermost channel
Not supported: Does not handle WebSocket event streams, server administration, or plugin management — use for the v4 REST surface (auth, users, teams, channels, posts) only.
Jentic publishes the only available OpenAPI specification for Mattermost API, keeping it validated and agent-ready. Mattermost is an open-source, self-hosted team-collaboration platform with HTTP and WebSocket APIs at `your-mattermost-url/api/v4`. The spec covers the core flows used by clients and bots: user authentication and identity, team and channel access, post creation, and basic file and preference operations. It is intended for developers building Mattermost integrations, internal bots, and AI agents that participate in Mattermost teams. Authentication uses bearer session tokens or personal access tokens.
Install Jentic One Beta
Connect the Mattermost API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Mattermost API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
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Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with Mattermost API.
Authenticate a user via login and obtain a session bearer token
Fetch the authenticated user's identity via the `me` endpoint
List teams and channels the authenticated user belongs to
Create posts in a Mattermost channel
Resolve user identity for downstream activity records
Bootstrap an integration's session against a Mattermost server URL
Use Cases
Patterns agents use Mattermost API for, with concrete tasks.
★ CI Status Bot
Engineering teams running self-hosted Mattermost want CI build statuses posted to a dedicated channel. The bot logs in once with a personal access token, fetches the right team and channel ID, and then creates posts whenever the CI pipeline emits a status. Posts typically include build URL, branch, and outcome.
Authenticate via `POST /users/login`, locate the channel id, then call `POST /posts` with the channel_id and the build summary message.
Identity-Aware Internal Tool
Internal admin tools running alongside Mattermost can use the chat session to identify the operator. The tool calls `GET /users/me` to confirm the logged-in user and uses the result to drive permissions in the tool itself, avoiding a separate auth system for internal-only utilities.
Call `GET /users/me` with the bearer token to retrieve the authenticated user's id, email, and role membership.
Team and Channel Discovery
Onboarding scripts that provision new bots or integrations need to enumerate teams and channels to find the correct destination. The `/teams` and `/channels` endpoints expose this listing, and a typical onboarding script caches the IDs locally so subsequent posts can skip the lookup step.
Call `GET /teams` followed by `GET /channels` to build a `{team_name → channel_ids}` map for the integration's config.
AI Agent in Mattermost
An AI agent that posts summaries or answers questions in a Mattermost channel can use Jentic to call the right operations on demand. Jentic stores the session or personal access token in the vault and exposes login, identity, and post operations via intent search, removing per-server auth boilerplate.
Search Jentic for 'post message to mattermost channel', load the `/posts` schema, and execute it with the channel_id and message body.
Key Endpoints
8 endpoints — jentic publishes the only available openapi specification for mattermost api, keeping it validated and agent-ready.
METHOD
PATH
DESCRIPTION
POST
/users/login
Authenticate and obtain a session token
GET
/users/me
Fetch the authenticated user
GET
/users
List users on the server
GET
/teams
List teams
GET
/channels
List channels
POST
/posts
Create a post in a channel
POST
/users/login
Authenticate and obtain a session token
GET
/users/me
Fetch the authenticated user
GET
/users
List users on the server
GET
/teams
List teams
GET
/channels
List channels
POST
/posts
Create a post in a channel
Why Jentic?
Three things that make agents converge on Jentic-routed access.
Credential isolation
Mattermost session and personal access tokens are stored encrypted in the Jentic vault (MAXsystem). Agents receive scoped session references and the `Authorization: Bearer ...` header is applied at execution time — raw tokens never enter the agent's context.
Intent-based discovery
Agents search by intent (e.g., 'post message to mattermost channel' or 'list mattermost teams') and Jentic returns the matching Mattermost operation with its input schema.
Time to first call
Direct Mattermost integration: 4-6 hours for login, token management, and post wiring. Through Jentic: under 30 minutes — search, load schema, execute.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using Mattermost API through Jentic.
Why is there no official OpenAPI spec for Mattermost API?
Mattermost publishes its API documentation as a custom site rather than a single OpenAPI document. Jentic generates and maintains an OpenAPI specification so AI agents and developers can call the Mattermost API via structured tooling. It is validated against the live API and kept up to date. Get started at https://app.jentic.com/sign-up.
What authentication does the Mattermost API use?
Mattermost uses HTTP bearer tokens in the `Authorization: Bearer ...` header. Tokens are issued either by `POST /users/login` (session token) or as personal access tokens generated in the Mattermost UI. Through Jentic, both are stored encrypted in the MAXsystem vault.
Can I post a message to a channel with the Mattermost API?
Yes. `POST /posts` creates a new post in a channel. Provide the `channel_id` and `message` body in the JSON payload, plus an optional `root_id` to make the post a reply within an existing thread.
What are the rate limits for the Mattermost API?
Mattermost rate limits are configured per server by the admin and enforced via `X-Ratelimit-Limit`, `X-Ratelimit-Remaining`, and `X-Ratelimit-Reset` response headers. The default is 10 requests per second per user; on `429 Too Many Requests`, back off until the reset window elapses.
How do I send a Mattermost post through Jentic?
Run `pip install jentic`, then use Jentic's search with the query 'post message to mattermost channel'. Jentic loads the `/posts` operation schema and your agent executes it with the channel_id and message — Jentic injects the bearer token automatically.
Does the API work against a self-hosted Mattermost server?
Yes. The base URL is parameterised as `https://{serverUrl}/api/v4`, so the same operations work against the public Mattermost cloud, an internal enterprise install, or a developer's local instance running on `http://localhost:8065`.
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