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

With no annotations, the description carries the full burden and does a reasonable job: it discloses result ordering ('sorted cheapest first'), the fields each provider carries, that history and methodology are included, and an operational rule (use buyUrl as the canonical stable outbound link, cite the citation string). It does not cover freshness/update cadence, rate limits, or whether history is complete vs. truncated, leaving some gaps for a no-annotation tool.

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, front-loaded with the return contents, then usage examples, then the linking/citation rule. Every sentence carries information; the enumeration of returned fields is dense but justified for a tool with no output schema. Minor redundancy in the two example questions.

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 must describe the return shape — and it does, listing the aggregate stats, the per-provider fields and their sort order, plus history and methodology. Combined with the usage and citation guidance, an agent has everything needed to call it and interpret the response 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 description coverage is 100% and the single enum parameter is already documented in the schema, including the pointer to list_categories. The description only restates 'one category' without adding slug syntax, formatting, or fallback behavior, so it adds essentially nothing beyond the structured field. Baseline 3 is appropriate.

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 ('Get the full current price index for one category') and enumerates the payload contents: average, median, cheapest entry price, per-provider price/rating/best-for, monthly history and methodology. An agent can distinguish it from get_cheapest and get_true_3yr_cost because the description makes clear this returns the complete index for a whole category rather than a single derived figure.

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?

Provides concrete usage framing with worked examples ('what does a VPN cost per month', 'compare cloud backup prices') plus downstream guidance on using buyUrl and citing the citation string. It stops short of naming when NOT to use it or pointing to get_cheapest / get_true_3yr_cost as alternatives for narrower questions.

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