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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the mutation profile is known. The description adds genuinely non-derivable behavior: the send is atomic with resolution, nothing is sent when the lookup is incomplete or multiple people match, and candidates are returned instead so the agent can ask the user. It does not cover auth/account-selection failure modes or rate limits, keeping it short of a 5.

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?

Front-loaded with the use case in the first clause, then the resolution rule, then the failure branch, then the guard against invented content. Four dense sentences, none redundant.

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 no output schema, the description carries the return-value burden and does explain the ambiguity return (candidates). It leaves the success response shape (e.g., message id, conversation reference) unspecified, but for a single-send tool with destructive annotations already present, that is a minor gap.

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. The description adds cross-parameter semantics the schema only implies per-field: that 'name' is resolved like messaging_resolve_recipient and that a send only proceeds on a unique match, which explains the interaction between name, recipient_user_id, and the ambiguity branch.

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 messaging message) and pins the scope precisely: a one-step resolve-and-send for voice-style requests, distinct from the two-step messaging_resolve_recipient + messaging_send_message path. An agent can tell it apart from whatsapp_send_message, instagram_send_message, and messaging_send_message 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?

Explicit when-to-use ('one-step send for voice-style requests') with a concrete example, an explicit when-not ('do not invent' the content; user must have stated it), and an alternative path implied by the reference to messaging_resolve_recipient and the schema note routing LinkedIn recipients to linkedin_resolve_person + linkedin_start_conversation. The ambiguity branch is fully described.

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