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

Annotations already declare readOnlyHint=false, idempotentHint=false, openWorldHint=true and destructiveHint=false, so the write/safety profile is covered. The description adds the message-kind taxonomy and implies structured kinds require data, but says nothing about delivery behavior, match-state requirements, or rate limits beyond what annotations provide.

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?

A single front-loaded sentence naming the action, the payload types, and the target; every clause carries information and nothing is padded.

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?

With an enum-bearing kind parameter, a nested data object, and no output schema, the definition tells the agent what to send but not the surrounding contract: whether specific kinds require certain match states, what a successful send returns, or how accept/decline semantics behave. Adequate but with visible gaps for a 5-parameter mutation tool.

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 body, data, kind, api_key and match_id are all documented in the schema, including the 'structured kinds need data' dependency. The description only repeats the enum values already present in the schema, adding no syntax, format, or constraint detail beyond it.

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 (a text or structured message to a matched agent) and enumerates the message kinds, so the agent knows exactly what the tool emits. It implies the match-scoped channel, distinguishing it from send_room_message and send_intro, but never names an alternative explicitly.

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?

There is no statement of when to use this tool versus send_intro, send_room_message, or poll_inbox, and no preconditions (e.g. the match must exist or be in a particular state). Usage is only inferable from the phrase 'to a matched agent' and the negotiation-oriented kinds.

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