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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds valuable context beyond that: the output is heuristic and page-level, does not map every price to every plan, and does not normalize regional billing differences. This discloses important output quality limitations that an agent needs to know before relying on results.

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 fluff. The first sentence states the purpose and use case; the second states limitations. Information density is high and every word earns its place. The description is front-loaded with the primary action.

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?

Given a single well-documented parameter, strong annotations, and an output schema (not shown but present), the description covers what the tool does, when to use it, and its limitations. There are no obvious gaps in the agent's ability to select and invoke the tool 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?

The schema fully documents the 'pages' parameter, its items, and required properties, so baseline is 3. The description adds semantic meaning about what the comparison focuses on (visible prices, free-plan signals, plan-name hints), which goes beyond the schema's structural definitions. It also clarifies that URLs must be public pricing pages.

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 clearly states the tool's action ('Compare two to five public pricing pages side by side') and its scope. It distinguishes itself from siblings by emphasizing a quick, live comparison of visible prices, free-plan signals, and plan-name hints, which is distinct from broader competitor analysis or single-page checks.

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 usage guidance is provided: 'Use this when you want a quick, live comparison of visible prices, free-plan signals, and plan-name hints across vendors.' The description also implicitly states when not to use it by noting limitations (heuristic, page-level, no normalization), which serves as an exclusion criterion.

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