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

Beyond the readOnlyHint=false annotation, it discloses two behavioral facts an agent could not infer: the message is attributed to an AI agent (irreversible provenance for the recipient) and the call needs the chat:write scope. It says nothing about rate limits or what dry_run does.

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?

Two short sentences, both earning their place, with the core action front-loaded and the auth requirement trailing.

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?

Covered: the write nature, AI attribution, and auth scope. Missing: any meaning for dry_run or conversation_id, and no indication of error behavior for a mutation tool with no output schema. Adequate but gapped.

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 0% and the description explains none of the three parameters. content and conversation_id are at least named by their presence in the schema, but dry_run is a non-obvious boolean that goes completely unexplained.

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+resource ('Send a chat message') and adds a distinguishing trait ('for the human', 'labelled as coming from an AI agent'). It doesn't name a sibling, but the send-vs-read split against read_messages is obvious.

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?

It gives a real prerequisite ('Requires the chat:write scope'), which tells the agent when the call will succeed, but offers no guidance on when to choose this over read_messages or list_conversations.

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