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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description goes well beyond them: it discloses the exact return payload (html, plain text, edit_url, install steps), the free-plan ceiling (four layouts, six accent colours, no logo/photo), and the injected 'Created with ProSignature' credit line. The deterministic 'same bytes' claim and the explicit no-storage guarantee are genuinely useful behavioral facts.

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?

Purpose and output are front-loaded in the first two sentences, and each following clause adds a distinct constraint (free-plan limits, credit line, statelessness). It is dense and reads as a long block rather than cleanly separated lines, which costs a point but no sentence is 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?

With no output schema, the description carries the return-value burden and does so completely: payload keys, plan-level limitations, branding injection, and the absence of side effects. An agent has everything needed to call it and interpret the result.

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 schema already documents all eight parameters, including the colour default and enum. The description only echoes a subset of that ('four layouts, six accent colours') without adding format or combination guidance, so 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 states a specific verb and resource ('Builds the email-safe HTML signature'), names the output artifact form (table + inline styles) and scopes it to 'one person'. It implicitly distinguishes itself from siblings like get_install_steps and list_layouts by explaining that install steps are bundled in the return rather than fetched separately.

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?

It establishes context ('free plan', 'no account', 'Nothing is installed or stored') so an agent knows this is a safe generation call, but it never states when to prefer this tool over siblings such as quote_price or get_install_steps. Usage is implied rather than instructed.

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