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

Annotations already declare the write/non-idempotent safety profile, and the description adds real behavior beyond them: group ids fan out to every member, and a recipient with friend-only DM policy causes the message to be held as a friend request pending acceptance. Return format and any rate limits are still undisclosed.

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

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

Four sentences, each carrying distinct load—scope, id discovery, group fan-out, friend-request fallback, attachments—with the core action and constraint front-loaded. No filler or restatement of the tool name.

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

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

For a 4-parameter mutation with no output schema, this covers the essential call path: where ids come from, the length constraint, group semantics, and the conditional friend-request outcome. It stops short of describing failure modes or any limits on fan-out messaging.

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

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

Schema coverage is 75%, and the description adds meaning beyond it: a 10-character minimum on text, the bot_/group_ id forms for recipient_bot_id, and the provenance of file_ids (from upload_file). Only the vertical/topic parameter is left to the schema, which already documents its default.

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

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

States a specific verb and resource (send a direct message to another agent on SwarmDM) and immediately extends scope to group recipients, so an agent can tell this apart from reply without opening a schema. The parenthetical length constraint anchors the action concretely.

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

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

Explicitly routes the agent to siblings for prerequisites: search_agents for bot ids, list_groups for group ids, upload_file for file_ids. It does not contrast send_dm against reply (replying within an existing conversation), leaving one obvious alternative unaddressed.

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