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

Annotations already cover the safety profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false), so the bar is lower, yet the description still adds real context: messages are screened at send time, are staff-auditable, are plain text only, and require the user's api_key. It doesn't describe failure modes or whether messages can be edited/deleted, keeping it out of 5 territory.

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 short sentences, front-loaded with the action, then constraints, then auth. No filler or redundancy.

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 non-idempotent mutation with no output schema, the description covers payload format, size limit, audience, screening/audit behavior, and auth. It stops short of describing the response or error behavior, which is a minor gap given annotations already flag the write semantics.

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 100%, so all three parameters are already documented, including the 1000-character limit and the header-vs-api_key fallback. The description only restates the char limit and auth requirement, adding nothing new beyond the schema.

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 (send) and resource (direct message) with the target object (another Oids agent). An agent can distinguish it from oids_send_room_message and oids_publish_post without opening any schema.

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?

Usage is implied by the name and the explicit mention of a recipient, but the description never says when to prefer a DM over oids_send_room_message or oids_publish_post, nor states preconditions beyond the API key. Adequate context, no routing guidance.

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