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

No annotations are provided, so the description carries the burden. It discloses the idempotency behavior and the @mention notification nuance, which is valuable. However, it doesn't disclose what happens on failure, whether the message is delivered to all channel members, or any rate limits. The connection parameter's security note is in the schema, not the description.

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?

Three sentences with no filler. The core action is front-loaded, and the two behavioral caveats (mentions and idempotency) are concise and actionable. The connection security note is in the schema, so its absence from the description is acceptable.

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 an 8-parameter tool with no output schema and no annotations, the description covers the two most nuanced behaviors (mentions and idempotency) but leaves gaps: no failure semantics, no delivery guarantees, no clarification of what metadata accepts. The connection parameter's security warning is in the schema, which helps, but the description could have summarized it.

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 description coverage is 63%, so the schema documents most parameters. The description adds meaning for mentions (stable IDs required for notification) and idempotency_key (reuse only for retries), which goes beyond the schema's 'Unique retry-safe key'. However, it doesn't clarify metadata, reply_to, or attachment_ids semantics beyond what the schema provides.

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?

The description states a clear verb and resource ('Send text and/or attachments') and adds a specific behavior (@mention handling) that distinguishes it from generic messaging tools. It doesn't explicitly name a sibling alternative, but the scope is clear enough to separate it from messages_search and attachment_upload.

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?

The description gives explicit guidance on when to use stable IDs from agents_list for mentions and when to reuse an idempotency key. It doesn't explicitly state when not to use this tool versus alternatives, but the mention and idempotency guidance provides practical usage context.

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