mail_update_draft

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

Annotations provide no guidance (readOnlyHint=false, destructiveHint=false), so the description must carry the burden. It states 'update fields' indicating a mutation, but does not disclose side effects (e.g., does it replace all fields or merge?), required permissions, or what happens if the session is not open. Some behavioral context is provided but insufficient.

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?

A single sentence of 11 words, front-loaded with the action 'Update fields'. No redundant words, very concise.

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?

The description is too brief given the tool's complexity: 8 parameters (including nuanced ones like fromAddress with multi-account fallback and attachmentPaths with unverified insertion), no output schema, and no mention of return value or error conditions. Essential context is missing.

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 only 38% (low). The description only lists subject/content/recipients, ignoring fromAddress and attachmentPaths which have important details in the schema. It does not add meaning beyond what the schema already provides for the mentioned parameters, and fails to compensate for the low schema coverage.

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 clearly states the verb (Update), the resource (fields of an open draft compose session), and the identifier (composeSessionId). It distinguishes from sibling tools like mail_create_draft or mail_delete_draft.

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?

The description makes it clear that this tool is for updating an existing draft session. While it doesn't explicitly state when not to use it or provide alternatives, the context of sibling tools provides differentiation. Could be improved by mentioning prerequisites like composeSessionId validity.

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