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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: the catalog is authoritative and changes over time, domain rate factors are always pass-through 1.0, email is 12-month-only with no multi-year promise, and there are hard constraints on framing vocabulary.

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 action and the trigger, followed by shape and math sections that earn their place. It is dense but slightly redundant with two 'CRITICAL' blocks and a repeated framing warning, which costs it a point.

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?

There is no output schema, so the description supplies the return shape, the per-category structure, the rate-factor math, and the domain/email exceptions. That is exactly what an agent needs to call it and use the result 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?

Zero input parameters, so there is nothing to document on the input side and the baseline of 4 applies. The description usefully redirects that space into describing the return shape and math instead.

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?

Specific verb + resource: 'Fetch the canonical Squish billing-term catalog.' It immediately distinguishes itself from catalog siblings (get_hosting_catalog, get_public_pricing) by declaring this is the rate-factor/term source of truth.

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 trigger: 'CALL THIS before quoting ANY multi-year rate (2-year, 3-year hosting; 2-10 year domain registration).' It also names the prohibited alternative ('never quote a rate factor or percentage from memory') and constrains email to 12-month quotes only.

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