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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantial behavior beyond them: it returns empty HTML for unpublished signatures, and returns 404 (no such email) versus 422 (not a recipient) for ineligible recipients. These failure modes and lifecycle constraints are exactly the kind of context annotations cannot express.

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 core action before the caveats, and every sentence carries distinct information (non-preview, publish prerequisite, empty-HTML case, error codes, alternative tool). The heavy ALL-CAPS emphasis and stacked parenthetical references make it denser than it needs to be, but there is no filler.

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?

An output schema exists, so return-value documentation is not the description's job, and the description still covers prerequisites, eligibility, error behavior and the alternative tool. For a 3-parameter read tool with full schema coverage and annotations, nothing an agent needs to call it correctly 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 100%, so the baseline is 3, and the schema already documents id, email_id and context. The description adds meaning by tying email_id to a recipient-membership requirement and its error consequences, which goes beyond the schema's 'UUID of a recipient email'. It does not add format or syntax detail beyond that, so a 4 rather than a 5.

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 ('get the REAL final installed HTML of a signature for a SPECIFIC recipient') and immediately scopes it as live published content rendered with the teammate's real values. It explicitly distinguishes itself from the nearest sibling by declaring 'This is NOT a preview' and naming preview_signature. An agent can differentiate it from preview_signature and list_signature_installations 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 an explicit prerequisite (publish_signature must run first), an eligibility constraint (the email must be a recipient — see list_signature_recipients), and a named alternative with the condition that selects it ('For a tracking-free placeholder layout check of a draft before publishing, use preview_signature instead'). When-to-use, when-not-to-use and the alternative are all covered.

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