Send Gmail email

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

Annotations already flag destructiveHint=true and idempotentHint=false, but the description goes well beyond them: it warns this actually sends (not a draft), recommends user confirmation, guarantees no silent send-to-draft conversion, discloses that idempotency_key is unenforced in v1, states recipients/content are not modified, and enumerates failure codes. This is rich behavioral context layered on top of structured hints.

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-loads the critical side-effect warning before details, which is the right priority order. It is somewhat long due to the full failure-code list, but each section (usage, params, success, failures) earns its place.

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 send tool with no output schema, the description supplies the return shape (message_id, thread_id, provider) and the failure taxonomy, covering both success and error paths. An agent has everything needed to call it and interpret results.

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 coverage is 100%, so the schema documents each parameter; baseline would be 3. The description adds real value by calling out required vs optional sets and, crucially, clarifying that idempotency_key is reserved and not enforced in v1 — a nuance the schema only hints at.

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') plus resource ('email through Gmail') and the acting identity ('authenticated Google account'). It explicitly distinguishes itself from the sibling gmail_create_draft, so an agent can route correctly without opening either 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?

Gives an explicit 'When to use' section: only when the user wants delivery now, plus a negative condition ('do not use this to prepare') and the named alternative (gmail_create_draft). Nothing is left to inference.

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