Signature

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

Annotations already signal non-read-only, idempotent, and non-destructive traits. The description adds non-obvious behavioral details: the signature is appended on send/reply/forward/draft/scheduled mail, and setting it overrides Gmail auto-import by marking the source 'manual'. These are useful disclosures beyond what annotations provide.

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?

The description is three concise sentences with no filler. It front-loads the core operation, then adds only high-value behavioral and permission context, earning each sentence's 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?

The description covers authentication needs, side effects, and the server's signature behavior, while the detailed input schema covers parameter semantics, conditional constraints, and defaults. No output schema exists, but the 'action' parameter already documents what 'get' returns, so the definition is sufficiently complete for an agent to invoke it correctly.

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 each parameter already has a meaningful description including enum values, defaults, and conditional constraints. The tool description does not need to add per-parameter semantics, so the baseline of 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?

The description states a specific verb and resource: 'Read or set an inbox's signature', and adds clarifying behavioral context about server-side appending. This distinguishes it from sibling tools like email_read, email_compose, or draft, none of which manage signatures.

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 gives clear operation-specific context: 'get' needs read:email, 'set' needs send:email, and setting marks the source as 'manual', overriding Gmail auto-import. It doesn't explicitly name alternative tools, but no sibling appears to overlap with signature management, so the guidance is clear enough.

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