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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, but the description adds genuinely new behavioral context: nothing is persisted, no account is required, and the caller receives HTML, plain text, and an edit link. It does not describe rate limits or any failure modes, keeping it just short of a 5.

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, front-loaded with purpose and return format, then routing rules. Slightly redundant in re-enumerating eight fields that the schema already names, but nothing is padded or off-topic.

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?

With no output schema, the description carries the return-value burden and does so — HTML, plain text, and an edit link are all described. Combined with the explicit sibling routing, an agent has everything needed to call this 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%, so every parameter including the layout enum and hex color pattern is already documented in the schema. The description only re-lists the field names and adds no format, default, or constraint detail beyond the schema, so the baseline 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 opens with a specific verb+resource ("Make a free email signature") and enumerates the inputs, so there is no ambiguity about what it produces. It also names the two sibling tools it is not — update_my_signature and get_signature — letting an agent distinguish it without reading schemas.

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?

Explicit routing is provided: saving to an account routes to update_my_signature, retrieving an already-saved signature routes to get_signature. The condition that selects each alternative is stated verbatim with example user phrasings ("create my signature", "save it").

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