Send an email

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

Annotations declare the safety profile (readOnly=false, destructive=false, openWorld=true), and the description adds the trait that matters most: dispatch happens immediately with no undo step, so consent must be secured first. It does not mention rate limits, send quotas, or what happens on delivery failure, which keeps 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?

Two sentences, no filler. The capability statement comes first and the safety constraint second, so the agent reads the routing rule before the guardrail.

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 nine-parameter outbound-mutation tool the schema carries all field detail, and the description covers the two things the schema cannot: when to send and the requirement to confirm first. The only real gap is the absence of a stated fallback to create_draft when the user has not yet confirmed.

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 every parameter, including reply_all and reply_to_message_id semantics, is already documented there. The description only echoes the recipient/subject/body trio during the confirmation instruction, adding no new meaning beyond the schema, so the baseline 3 applies.

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 and resource ("Send a message") and covers both modes (new or reply), so an agent knows exactly what the tool produces. The word "immediately" implicitly separates it from the draft-creating siblings, but no sibling is named, so differentiation is left to inference.

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 gating condition — only after the user explicitly asked to send — plus a confirmation prerequisite covering recipients, subject and body. It does not name the alternative path (create_draft / send_draft) for the case where the user has not confirmed, which would have made routing unambiguous.

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