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

Annotations already declare the destructive/non-idempotent/closed-world profile, so the bar is lower, and the description still adds two genuinely useful facts: the message is visible to other conversation members, and requestId must be preserved on retries. 'Preserve requestId on retries' is consistent with idempotentHint=false rather than contradicting it, since the key exists precisely because the raw call is not idempotent. It does not explain failure or partial-success behavior.

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?

Four short sentences, front-loaded with the action and immediately followed by the guardrail, visibility note, and retry rule. No sentence is redundant filler.

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 output schema present and annotations covering the safety profile, the description supplies the remaining essentials: intent scope, ambiguity guardrail, audience visibility, and retry identity. Only minor gaps remain, such as what happens when the destination is inaccessible or the send fails.

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%, and the schema already documents body, chat.id, chat.kind, and requestId reuse semantics. The description's retry note on requestId merely mirrors what the schema property description already states, so nothing new is added. Baseline 3 applies when the schema does the heavy lifting.

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 names a specific verb and resource ('Send the message ... to a specified accessible conversation'), which makes it trivially distinguishable from read-oriented siblings like read_messages and list_conversations. The scoping phrase 'explicitly requested by the user' further narrows intent beyond a generic send.

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 clear precondition for when to act ('explicitly requested by the user') and an explicit when-not/verify rule ('Confirm ambiguous destinations or wording before calling'). It stops short of naming alternatives (e.g., using list_conversations to resolve a destination), so it is clear context without full routing guidance.

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