Basecamp 3 API

Name: Basecamp 3 API API
Brand: Basecamp 3 API
Availability: InStock

★ Only Publicly Available OpenAPI DocumentProductivityCollaborationbearer74 EndpointsREST

For Agents

Create and update Basecamp 3 projects, to-dos, messages, documents, and comments, list people on a project, and post into Campfire chats using OAuth 2.0 bearer auth.

Quickstart

Get started with Basecamp 3 API in minutes using your preferred integration method.

# Add to your MCP client config (Claude Desktop, Cursor, Windsurf)
{
  "jentic": {
    "url": "https://api.jentic.com/mcp",
    "auth": "oauth"
  }
}

# Then ask your agent:
"create a basecamp todo"

# → Jentic returns the GET /events tool with parameter schema, agent executes.

Capabilities

What an agent can do with Basecamp 3 API API.

Create and update Basecamp projects, including archiving and trashing through status filters

Manage to-do lists and individual to-dos — create, complete, uncomplete, reposition, and assign people

Post and update messages on a project's message board with rich-text HTML content

List and grant or revoke project access for specific people via the project users endpoint

GET STARTED

Start building with Basecamp 3 API API

Explore with Jentic

View OpenAPI Document

Jentic publishes the only available OpenAPI document for Basecamp 3 API, keeping it validated and agent-ready.

Jentic publishes the only available OpenAPI specification for Basecamp 3 API, keeping it validated and agent-ready. The Basecamp 3 API is a JSON REST interface to Basecamp's project management workspace, covering projects, message boards, to-do sets, to-dos, people, comments, documents, vaults, Campfires, schedules, uploads, webhooks, and recordings. All requests are scoped to an account ID in the base URL and authenticated with an OAuth 2.0 bearer token. The spec exposes 74 endpoints across 24 resource tags, enough to drive most workflow automation that Basecamp users do in the UI.

Use Cases

Patterns agents use Basecamp 3 API API for, with concrete tasks.

★ Client Project Bootstrapping

When onboarding a new client, automatically create a Basecamp project, populate an initial to-do list, post a kick-off message, and grant the client team members access. POST /projects.json creates the project, POST /todosets/{todoSetId}/todolists.json adds the list, and PUT /projects/{projectId}/people/users.json grants access in a single workflow rather than clicking through the UI.

Create a Basecamp project named 'Acme Q3 Redesign', add a to-do list 'Kickoff', create the to-dos 'Send brief', 'Schedule kickoff call', and 'Confirm scope', and grant access to two emails.

Status Reporting From To-Dos

Pull current to-do state from Basecamp to feed an external dashboard or weekly status email. GET /todolists/{todoListId}/todos.json with completed=true or completed=false returns to-dos by completion state so a reporting job can compute on-time vs overdue counts without scraping the UI.

For project ID 12345, fetch all to-do lists, then list completed and outstanding to-dos for each, and produce a weekly summary email.

Cross-Tool Message Mirroring

Mirror messages posted in Slack or another chat tool into a Basecamp project's message board so durable decisions live alongside the work. POST /message_boards/{messageBoardId}/messages.json accepts a subject and HTML body, and POST /recordings/{recordingId}/comments.json lets follow-ups land as threaded comments.

Post a message titled 'Decision: API contract approved' with a one-paragraph HTML body to message board 5678, then attach a comment summarising the next step.

AI Agent Project Operations

Let an AI agent run routine Basecamp operations — create to-dos from a meeting transcript, archive completed projects, post weekly recaps — through Jentic. The agent searches for the operation by intent, loads the spec, and executes; OAuth tokens stay isolated in Jentic's vault.

Through Jentic, search 'create a basecamp todo', load the createTodo schema, and add follow-up to-dos to list 9876 from a meeting transcript.

Key Endpoints

74 endpoints — jentic publishes the only available openapi specification for basecamp 3 api, keeping it validated and agent-ready.

METHOD

PATH

DESCRIPTION

POST

/projects.json

Create a new project

GET

/projects.json

List all projects

POST

/todolists/{todoListId}/todos.json

Create a to-do in a list

POST

/todos/{todoId}/completion.json

Mark a to-do complete

POST

/message_boards/{messageBoardId}/messages.json

Post a message to a board

POST

/recordings/{recordingId}/comments.json

Add a comment to a recording

PUT

/projects/{projectId}/people/users.json

Grant or revoke project access

POST

/projects.json

Create a new project

GET

/projects.json

List all projects

POST

/todolists/{todoListId}/todos.json

Create a to-do in a list

POST

/todos/{todoId}/completion.json

Mark a to-do complete

POST

/message_boards/{messageBoardId}/messages.json

Post a message to a board

Why though Jentic?

Three things that make agents converge on Jentic-routed access.

Credential isolation

Basecamp 3 OAuth 2.0 access and refresh tokens are stored encrypted in the Jentic vault. Agents call createProject, createTodo, and other operations through Jentic, which injects the bearer token at execution and refreshes it transparently — secrets never enter the agent's context.

Intent-based discovery

Agents search Jentic by intent (e.g., 'create a basecamp todo' or 'post a basecamp message') and Jentic returns the matching Basecamp 3 operation with its input schema, so the agent calls the right endpoint without browsing bc3-api docs.

Time to first call

Direct Basecamp 3 integration: 2-4 days for OAuth setup, account-ID handling, rate-limit retries, and resource modelling. Through Jentic: under 1 hour — search, load, execute.

Related APIs

Alternatives and complements available in the Jentic catalogue.

Alternative

Asana API

Asana offers a richer task hierarchy with sections, custom fields, and portfolios for larger product teams.

Pick Asana when teams need custom fields, portfolios, or workflow rules; pick Basecamp 3 for a flatter project-and-todo model with built-in Campfires and message boards.

Alternative

Trello API

Trello uses a board-and-card model rather than Basecamp's project-and-todo-list structure.

Use Trello when the workflow is naturally Kanban; use Basecamp when the team wants threaded discussions, documents, and to-dos in one place.

Alternative

Linear API

Linear targets engineering issue tracking with cycles and triage queues rather than general project management.

Pick Linear for software issue tracking; Basecamp for cross-functional project management with clients.

Complementary

Slack API

Mirror Slack threads into Basecamp messages or comments so decisions persist alongside the work.

Use Slack alongside Basecamp when realtime chat happens in Slack but durable decisions, files, and to-dos must live with the project.

FAQs

Specific to using Basecamp 3 API API through Jentic.

Why is there no official OpenAPI spec for Basecamp 3 API?

Basecamp publishes Markdown reference docs at github.com/basecamp/bc3-api but no OpenAPI specification. Jentic generates and maintains this spec so that AI agents and developers can call Basecamp 3 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 Basecamp 3 API use?

Basecamp 3 uses OAuth 2.0 bearer tokens, sent in the Authorization header. Through Jentic, OAuth tokens are stored encrypted in the vault and refreshed automatically, so the agent never handles raw client secrets or refresh tokens.

Can I create and complete to-dos with the Basecamp 3 API?

Yes. POST /todolists/{todoListId}/todos.json creates a to-do with content, due date, and assignees, POST /todos/{todoId}/completion.json marks it complete, and DELETE /todos/{todoId}/completion.json reopens it. Repositioning is handled by PUT /todos/{todoId}/position.json.

What are the rate limits for the Basecamp 3 API?

Basecamp enforces a documented limit of 50 requests per 10-second window per access token; exceeding it returns 429 Too Many Requests with a Retry-After header. Build retries with exponential backoff and respect Retry-After when calling at scale.

How do I post a message to a Basecamp project through Jentic?

Run pip install jentic, then search 'post a basecamp message', load the createMessage operation, supply messageBoardId plus a subject and HTML content body, and execute. Sign up at https://app.jentic.com/sign-up to receive an agent API key.

Does the Basecamp 3 API require an account ID in every request?

Yes. The base URL is https://3.basecampapi.com/{accountId}, and every endpoint path is appended to that account-scoped prefix. The account ID is returned alongside the access token during the OAuth 2.0 authorisation flow.