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

With no annotations, the description carries the disclosure burden. It reveals concrete behavioral traits: output is tables-only with inline CSS and fixed widths, Gmail rejects base64 images, and the free output appends a credit line. This goes well beyond the name, though it doesn't discuss failure/error behavior.

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?

Three sentences with no filler: the first front-loads the action, the second layers on compatibility constraints, and the third handles pricing/next step. Every sentence earns its 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?

For a tool with 14 parameters and no output schema/annotations, the description covers the core behavior and key constraints but leaves out defaults, template selection details, and error scenarios. It is adequate for a basic call with full_name, but not complete for advanced usage.

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 43%, but the description does not compensate. It mentions absolute-URL images and the credit line, which loosely maps to photo_url and language, yet most parameters (city, phone, company, website, socials, accent_color) receive no additional semantics beyond their field names.

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 opens with a specific verb and resource: 'Build ready-to-paste email-signature HTML from a person's details.' This clearly differentiates it from siblings like check_email_signature and email_client_compatibility_matrix, since it's about generating rather than verifying or comparing.

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 the generation use case explicit and even routes to get_pricing when someone wants to remove the credit line. It doesn't explicitly exclude alternatives, but the build-vs-check/compatibility/list split is evident from the wording.

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