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

Annotations already establish a safe read-only, closed-world operation, and the description reinforces that with 'no live lookup' and 'free cached'. It adds real value beyond annotations: unknown costs are not fabricated, observed dates and cautions are included, and the Webshare affiliate link is disclosed. Return-shape and staleness thresholds are still implicit.

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?

Four dense sentences with no filler, and the core purpose is front-loaded ahead of the caveats. The telegraphic phrasing ('Full captured package bills only', 'unknown costs stay unknown') is efficient but slightly terse for first-time readers.

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 covers what the comparison returns (observed dates, sources, cautions, disclosed affiliate link) and what it excludes. It is largely complete for a read-only cached pricing tool, though it doesn't explain ordering or how offers are ranked.

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 coverage is 0%, so the description carries the burden, and it does name both parameters plus the 'positive' constraint on monthly_gb. However, it omits the enum values (residential, datacenter, isp_static_residential, mobile) and any unit/precision guidance for GB, leaving half the semantic load on the schema.

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?

States a specific verb and resource: comparing proxy pricing offers, filtered by product type and monthly GB. Its domain is clearly distinct from siblings like compare_scraping_apis and compare_rag_extractors, but it never explicitly names or routes away from them, so the differentiation is inferred rather than stated.

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?

Strong scoping signals: free cached data, no live lookup, full captured package bills only, per-IP offers handled separately. That tells the agent when this tool's output is appropriate, but it gives no explicit when-to-use-vs-alternative routing.

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