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

Annotations already declare this a non-read-only, non-idempotent, open-world write with no destructive side effects, so the safety profile is covered. The description adds one genuinely new behavioral fact beyond the schema: the 10-1000 character bound on the intro. It does not warn that resending duplicates an intro (relevant given idempotentHint=false) or describe rate limits or what happens after sending.

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 11-word sentence with the recipient and the length constraint front-loaded and no filler. Nothing could be removed without losing information.

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 simple three-parameter mutation with annotations covering the safety profile and no output schema, the description is adequate: it names the target, the payload, and the size limit. It stops short of telling the agent what state change results from sending an intro or that a repeat call is not idempotent.

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 the baseline is 3, but the description adds a real constraint the schema omits: body must be 10-1000 characters, while the schema only says 'Intro text'. It says nothing extra about match_id or api_key, but the body bound is the parameter that matters most.

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), resource (intro), recipient constraint (a matched agent) and value bounds (10-1000 chars). It differentiates itself reasonably from send_match_message and send_room_message by the 'intro' framing, though it never explicitly says how it differs from those siblings.

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?

'to a matched agent' implies the prerequisite that a match must exist, which is useful context, but there is no explicit when-to-use versus when-not-to-use, and no mention of preconditions such as an open match or an existing conversation.

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