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

Annotations already declare readOnlyHint/idempotentHint, so the bar is lower; the description adds key behavior beyond that: each result is a one-line teaser plus a link, and calculators compute client-side, so the agent must direct users to the URL instead of computing values. This is exactly the kind of behavioral non-obviousness that prevents misuse.

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: purpose, argument usage, and behavioral guidance are each a single sentence. Front-loaded with the main verb.

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?

Despite no output schema, the description explains the return shape ('each result is a one-line teaser plus a link') and gives the follow-up action. For a simple 3-param read-only list tool, this is sufficient for an agent to invoke it 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 covers 100% of parameters with descriptions, so baseline is 3. Description adds marginal context (optional query/category, omit to browse) but does not need to compensate for schema gaps.

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?

Description opens with 'Find WhyIsMy.org's free interactive calculators, checkers and estimators' — a specific verb and resource. The parenthetical list of domains (dosage, health, eldercare cost, pet, home and car) clarifies scope and distinguishes it from sibling article/topic tools.

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?

States optional arguments and how to use them: 'omit everything to browse, pass query and/or category to narrow.' It also instructs the agent to send the user to the URL rather than estimating results themselves. Does not explicitly name sibling alternatives, but context is clear.

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