Basecamp MCP Server

Create Basecamp Message

basecamp_create_message

Creates a new message in a Basecamp message board, with optional content and publish status.

Instructions

Create a new message in a Basecamp message board.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`status`	No	Message status. Use "active" to publish, "drafted" to save as an unpublished draft.	active
`content`	No	HTML message content. HTML rules for content: * Allowed tags: p, span, h2, h3, h4, br, strong, em, strike, code, a (with href attribute), pre, ol, ul, li, blockquote, mark, figure, figcaption, table, tbody, tr, th, td, div, bc-attachment. * Use <p> for paragraphs. Use <p><br></p> for empty line spacing between paragraphs. * Headings: use <h2>, <h3>, <h4> as appropriate. * Inline code: <code>text</code>. Preformatted blocks: <pre>text</pre>. * Ordered lists: <ol><li>...</li></ol>. Unordered: <ul><li>...</li></ul>. * Tables: <table><tbody><tr><th>Heading</th>...</tr><tr><td>Cell</td>...</tr></tbody></table> * To mention people: <bc-attachment sgid="{ person.attachable_sgid }" content-type="application/vnd.basecamp.mention"></bc-attachment> * Single image: <bc-attachment sgid="{ attachment.attachable_sgid }"></bc-attachment> * Image gallery: wrap multiple <bc-attachment sgid="..." presentation="gallery"> in a <div>. * Basecamp auto-enriches bc-attachment tags after saving (adds url, href, filename, content-type, etc.) — you never need to write those. * When you see an existing, already-enriched <bc-attachment> tag (e.g. from a previous list/get call), leave its inner HTML alone. Before any content_append/content_prepend/search_replace runs, it is automatically collapsed back to its minimal form (sgid, presentation, caption, and content-type for mentions) — you don't need to strip it yourself, and doing so manually is unnecessary and risks mismatched find strings. * Background highlights: <mark style="background-color: var(--highlight-bg-N);">...</mark> * Text color highlights: <span style="color: var(--highlight-N);">...</span> * For both, N is 1 (yellow), 2 (amber), 3 (red), 4 (pink), 5 (purple), 6 (blue), 7 (teal), 8 (near-white), or 9 (light gray).
`subject`	Yes	Message subject/title
`message_type_id`	No	Optional message type/category ID
`message_board_id`	Yes	Basecamp resource identifier

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv1.2.2Sep 9, 2026

changedInput schema / properties / content / description

Previous value: -"HTML message content. \n\nHTML rules for content:\n\n* Allowed tags: p, span, h2, h3, h4, br, strong, em, strike, code, a (with href attribute), pre, ol, ul, li, blockquote, mark, figure, figcaption, table, tbody, tr, th, td, div, bc-attachment.\n* Use <p> for paragraphs. Use <p><br></p> for empty line spacing between paragraphs.\n* Headings: use <h2>, <h3>, <h4> as appropriate.\n* Inline code: <code>text</code>. Preformatted blocks: <pre>text</pre>.\n* Ordered lists: <ol><li>...</li></ol>. Unordered: <ul><li>...</li></ul>.\n* Tables: <table><tbody><tr><th>Heading</th>...</tr><tr><td>Cell</td>...</tr></tbody></table>\n* To mention people: <bc-attachment sgid=\"{ person.attachable_sgid }\" content-type=\"application/vnd.basecamp.mention\"></bc-attachment>\n* Single image: <bc-attachment sgid=\"{ attachment.attachable_sgid }\"></bc-attachment>\n* Image gallery: wrap multiple <bc-attachment sgid=\"...\" presentation=\"gallery\"> in a <div>.\n* Basecamp auto-enriches bc-attachment tags after saving (adds url, href, filename, content-type, etc.) — you never need to write those.\n* To consume less tokens, existing <bc-attachment> tags can be rewritten keeping only: sgid, presentation, caption. For mentions also keep content-type=\"application/vnd.basecamp.mention\". Drop everything else including inner HTML.\n* Background highlights: <mark style=\"background-color: var(--highlight-bg-N);\">...</mark>\n* Text color highlights: <span style=\"color: var(--highlight-N);\">...</span>\n* For both, N is 1 (yellow), 2 (amber), 3 (red), 4 (pink), 5 (purple), 6 (blue), 7 (teal), 8 (near-white), or 9 (light gray).\n"New value: +"HTML message content. \n\nHTML rules for content:\n\n* Allowed tags: p, span, h2, h3, h4, br, strong, em, strike, code, a (with href attribute), pre, ol, ul, li, blockquote, mark, figure, figcaption, table, tbody, tr, th, td, div, bc-attachment.\n* Use <p> for paragraphs. Use <p><br></p> for empty line spacing between paragraphs.\n* Headings: use <h2>, <h3>, <h4> as appropriate.\n* Inline code: <code>text</code>. Preformatted blocks: <pre>text</pre>.\n* Ordered lists: <ol><li>...</li></ol>. Unordered: <ul><li>...</li></ul>.\n* Tables: <table><tbody><tr><th>Heading</th>...</tr><tr><td>Cell</td>...</tr></tbody></table>\n* To mention people: <bc-attachment sgid=\"{ person.attachable_sgid }\" content-type=\"application/vnd.basecamp.mention\"></bc-attachment>\n* Single image: <bc-attachment sgid=\"{ attachment.attachable_sgid }\"></bc-attachment>\n* Image gallery: wrap multiple <bc-attachment sgid=\"...\" presentation=\"gallery\"> in a <div>.\n* Basecamp auto-enriches bc-attachment tags after saving (adds url, href, filename, content-type, etc.) — you never need to write those.\n* When you see an existing, already-enriched <bc-attachment> tag (e.g. from a previous list/get call), leave its inner HTML alone. Before any content_append/content_prepend/search_replace runs, it is automatically collapsed back to its minimal form (sgid, presentation, caption, and content-type for mentions) — you don't need to strip it yourself, and doing so manually is unnecessary and risks mismatched find strings.\n* Background highlights: <mark style=\"background-color: var(--highlight-bg-N);\">...</mark>\n* Text color highlights: <span style=\"color: var(--highlight-N);\">...</span>\n* For both, N is 1 (yellow), 2 (amber), 3 (red), 4 (pink), 5 (purple), 6 (blue), 7 (teal), 8 (near-white), or 9 (light gray).\n"

Changed9 schema fields changedv1.2.1Jun 19, 2026

removedInput schema / properties / bucket_id

Removed value: -{
-  "description": "Basecamp resource identifier",
-  "type": "number"
-}

changedInput schema / properties / content / description

Previous value: -"HTML message content. To mention people: <bc-attachment sgid=\"{ person.attachable_sgid }\"></bc-attachment>"New value: +"HTML message content. \n\nHTML rules for content:\n\n* Allowed tags: p, span, h2, h3, h4, br, strong, em, strike, code, a (with href attribute), pre, ol, ul, li, blockquote, mark, figure, figcaption, table, tbody, tr, th, td, div, bc-attachment.\n* Use <p> for paragraphs. Use <p><br></p> for empty line spacing between paragraphs.\n* Headings: use <h2>, <h3>, <h4> as appropriate.\n* Inline code: <code>text</code>. Preformatted blocks: <pre>text</pre>.\n* Ordered lists: <ol><li>...</li></ol>. Unordered: <ul><li>...</li></ul>.\n* Tables: <table><tbody><tr><th>Heading</th>...</tr><tr><td>Cell</td>...</tr></tbody></table>\n* To mention people: <bc-attachment sgid=\"{ person.attachable_sgid }\" content-type=\"application/vnd.basecamp.mention\"></bc-attachment>\n* Single image: <bc-attachment sgid=\"{ attachment.attachable_sgid }\"></bc-attachment>\n* Image gallery: wrap multiple <bc-attachment sgid=\"...\" presentation=\"gallery\"> in a <div>.\n* Basecamp auto-enriches bc-attachment tags after saving (adds url, href, filename, content-type, etc.) — you never need to write those.\n* To consume less tokens, existing <bc-attachment> tags can be rewritten keeping only: sgid, presentation, caption. For mentions also keep content-type=\"application/vnd.basecamp.mention\". Drop everything else including inner HTML.\n* Background highlights: <mark style=\"background-color: var(--highlight-bg-N);\">...</mark>\n* Text color highlights: <span style=\"color: var(--highlight-N);\">...</span>\n* For both, N is 1 (yellow), 2 (amber), 3 (red), 4 (pink), 5 (purple), 6 (blue), 7 (teal), 8 (near-white), or 9 (light gray).\n"

removedInput schema / properties / message_board_id / $ref
```
Removed value: -"#/properties/bucket_id"
```
addedInput schema / properties / message_board_id / description
```
Added value: +"Basecamp resource identifier"
```
addedInput schema / properties / message_board_id / type
```
Added value: +"number"
```

changedInput schema / properties / message_type_id / $ref

Previous value: -"#/properties/bucket_id"New value: +"#/properties/message_board_id"

changedInput schema / properties / status / description

Previous value: -"Message status"New value: +"Message status. Use \"active\" to publish, \"drafted\" to save as an unpublished draft."

changedInput schema / properties / status / enum

Previous value: -[
-  "active",
-  "draft"
-]New value: +[
+  "active",
+  "drafted"
+]

changedInput schema / required

Previous value: -[
-  "bucket_id",
-  "message_board_id",
-  "subject"
-]New value: +[
+  "message_board_id",
+  "subject"
+]

Changed4 schema fields changedv1.0.0Jan 4, 2026

addedInput schema / $schema

Added value: +"http://json-schema.org/draft-07/schema#"

addedInput schema / additionalProperties
```
Added value: +false
```

changedInput schema / properties / content / description

Previous value: -"Message content (HTML supported)"New value: +"HTML message content. To mention people: <bc-attachment sgid=\"{ person.attachable_sgid }\"></bc-attachment>"

addedInput schema / properties / message_type_id

Added value: +{
+  "$ref": "#/properties/bucket_id",
+  "description": "Optional message type/category ID"
+}

First observedOct 25, 2025

TDQS

A3.8/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, establishing the operation as a non-destructive write. The description adds no further behavioral detail—such as whether the message becomes immediately visible—so transparency relies solely on the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single sentence that directly states the tool's purpose without unnecessary detail. It is appropriately sized for the simplicity of the operation, with the schema carrying the bulk of the detailed guidance.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description is minimal but sufficient given the comprehensive input schema and annotations. It does not mention required fields, but those are explicit in the schema, and there is no output schema to describe. Overall, the agent has enough context to invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

All five parameters are documented in the input schema with descriptions, including the enum for status and the detailed HTML content rules. The tool description itself does not add any parameter information beyond the schema, so parameter semantics are fully covered by the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific action ('Create a new message') and a target resource ('in a Basecamp message board'), clearly distinguishing it from list/get/update sibling tools like basecamp_list_messages and basecamp_update_message.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description does not explicitly mention when to use this tool compared to alternatives, but the verb 'Create' and the noun 'message' imply it is for new message creation. No explicit when-not or alternative references are present, so usage guidance is only implied through the tool's name and phrasing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server

Create Basecamp Message

Instructions

Input Schema

Schema Changelog

TDQS

Other Tools