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

Goes well beyond the annotations: it discloses that execution is asynchronous ('runs in the background', result lists what was queued), how to observe completion, and the full error surface (409 installed_by_client, 409 no_signature_to_install, 422 not_a_recipient, 403 plan limitation, 409 installation_unavailable), including the prescribed agent response for each. The annotations only flag it as a non-idempotent, destructive write.

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 action and its scope, then layers usage examples, then error handling — a logical order. It is dense and clause-heavy but nearly every sentence carries operational content; only the parenthetical integration list (Google Workspace, Zoho Mail, Front) is arguably expendable.

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 destructive, asynchronous, multi-error-path tool it covers what is needed: scope vs the sibling, async behavior and polling, and every documented failure with the expected relay message. An output schema exists, so the description is right not to explain return values.

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 email_id and signature_id semantics are already documented, and the description largely restates them ('or only `signature_id`', installed/activated vs published assignments). It adds the useful nuance that the scope is 'the installed (activated) and published signatures assigned to the email', but not enough beyond the schema to raise the baseline.

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 (install one email's signatures) and immediately bounds the scope: 'in its mailbox alone, without reinstalling the signature for everyone else (install_signature)'. An agent can distinguish it from the sibling install_signature and from the recipient-management tools without opening a 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 concrete when-to-use scenarios (a send-as alias needing a signature, one person whose title changed) and names the higher-scope alternative install_signature as the thing you should not reach for. It also spells out the operational follow-up (list_signature_installations with the email_id) and the conditions that produce each failure mode.

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