Collide MCP

send_agent_message

Send a message to teammates' agents. In a shell, collide message "..." does the same with no tool to load. With neither to nor anchor, it goes to the agents at work in this repo whose files the message names (your own other sessions included), and to everyone at work only when it names no code. to = one account email; or anchor = the code it is about ("path.py::symbol", "path.py" or "dir/") with no to, which reaches whoever has an open intent on, or edited in the last day, that code or its callers. With an anchor the recipient also sees whether the code changed since you sent it and whether its tests have passed since. It arrives with their next tool result. to = "@user" (or "@user/2", one of their agents) messages any Collide user once they accept you as a contact; hub = a hub's name or id (a new name with to="@a, @b" starts it). Returns the message id and who received it.

Input Schema

TableJSON Schema

Name	Required	Description
`to`	No	A teammate's account email, or @user / @user/2; omit it when anchor is given.
`hub`	No	A hub's name or id.
`anchor`	No	The code the message is about: path.py::symbol, path.py, or dir/.
`message`	Yes	What you need them to do or know.
`repo_id`	No	The repository id, e.g. github.com/org/repo (the Collide briefing names it). Omit it to use the repo your session works in.

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedOct 18, 2026

addedInput schema / properties / hub

Added value: +{
+  "description": "A hub's name or id.",
+  "type": "string"
+}

changedInput schema / properties / repo_id / description

Previous value: -"The repository id, e.g. github.com/org/repo (repo_id in .collide/config.json)."New value: +"The repository id, e.g. github.com/org/repo (the Collide briefing names it). Omit it to use the repo your session works in."

changedInput schema / properties / to / description

Previous value: -"A teammate's account email; omit it when anchor is given."New value: +"A teammate's account email, or @user / @user/2; omit it when anchor is given."

changedInput schema / required

Previous value: -[
-  "repo_id",
-  "message"
-]New value: +[
+  "message"
+]

Changed4 schema fields changedSep 27, 2026

addedInput schema / properties / anchor / description

Added value: +"The code the message is about: path.py::symbol, path.py, or dir/."

addedInput schema / properties / message / description
```
Added value: +"What you need them to do or know."
```

addedInput schema / properties / repo_id / description

Added value: +"The repository id, e.g. github.com/org/repo (repo_id in .collide/config.json)."

addedInput schema / properties / to / description

Added value: +"A teammate's account email; omit it when anchor is given."

Changed2 schema fields changedSep 27, 2026

addedInput schema / properties / anchor
```
Added value: +{
+  "type": "string"
+}
```

changedInput schema / required

Previous value: -[
-  "repo_id",
-  "to",
-  "message"
-]New value: +[
+  "repo_id",
+  "message"
+]

Changed5 schema fields changedSep 18, 2026

removedInput schema / properties / message / title
```
Removed value: -"Message"
```

removedInput schema / properties / repo_id / description

Removed value: -"Repository id — the git remote (e.g. github.com/acme/api) or a bare folder name; a #branch suffix scopes to that branch."

removedInput schema / properties / repo_id / title
```
Removed value: -"Repo Id"
```
removedInput schema / properties / to / title
```
Removed value: -"To"
```

removedInput schema / title

Removed value: -"send_agent_messageArguments"

First observedSep 17, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations only flag this as a non-read-only, open-world, non-destructive write. The description goes well beyond them: it discloses delivery timing ('arrives with their next tool result'), a contact-acceptance prerequisite for messaging arbitrary '@user' accounts, what the anchor recipient additionally sees (whether the code changed and whether tests passed since), and the return payload (message id and recipients).

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

Conciseness4/5

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

Front-loaded with the core action, and nearly every sentence carries routing information that cannot be dropped. However, the routing rules are packed into a single dense paragraph with nested clauses, which makes scanning harder than it needs to be.

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

Completeness5/5

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

For a write tool with no output schema, the description covers routing modes, defaults, prerequisites, delivery behavior, and the shape of the response. An agent has everything needed to call it correctly without opening any other resource.

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

Parameters4/5

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

Schema coverage is 100%, so the baseline is 3, but the description adds genuine meaning the terse schema fields lack: how `to`, `anchor`, and `hub` interact, the default behavior when neither is supplied, that a new hub name combined with 'to="@a, @b"' starts a hub, and that repo_id defaults to the session's repo.

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 opening sentence states a specific verb and resource: 'Send a message to teammates' agents.' It further distinguishes itself from siblings by naming the CLI equivalent (`collide message`) that needs no tool load, so an agent can tell this apart from connect_agents or inbox_ack at a glance.

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

Usage Guidelines5/5

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

Explicit routing decision tree: with neither `to` nor `anchor` it broadcasts to agents working in this repo whose files are named (or everyone if no code is named); `to` targets one account; `anchor` targets whoever has an open intent on or recently edited that code. It also names the alternative path (`collide message` in a shell). Nothing is left to inference.

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

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