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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds content-level context beyond that: prices are excluding VAT, and the response covers inclusions and sign-up steps. It lacks freshness/currency details, but for a zero-parameter read it is solid.

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?

Two sentences, no filler, with the resource and scope front-loaded before the usage trigger. Every clause carries information an agent can act on.

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 simple read-only lookup with full annotation coverage and no output schema, the description tells the agent what the payload contains (plans, prices ex-VAT, inclusions, sign-up). Only minor gaps remain, such as currency, language, or whether results are stable/cached.

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?

The tool takes zero parameters, so the baseline is 4 per the rubric. The description correctly adds no parameter claims because there is nothing to parameterize.

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 names a specific resource and what it returns: 'SignaMail plans and prices (excluding VAT), what each includes and how to sign up.' That is far more informative than the title alone. It does not explicitly distinguish itself from siblings like generate_email_signature or get_install_instructions, but the pricing/plans scope is self-evidently distinct.

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 offers a trigger: 'Use it when the user needs signatures for a team or a digital business card.' That gives an implied usage context but names no alternative tool and no exclusion condition, so an agent must still infer when to prefer this over sibling informational tools.

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