model_price_history

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered. The description adds genuine context about data provenance (archived copies since 2023) and what the output includes (per-change % and overall change), but says nothing about rate limits, coverage gaps, or freshness beyond 'today's price'.

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 tight sentences, front-loaded with the resource and time scope, then the returned content. No filler or repetition of the tool name.

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?

An output schema exists, so return-value explanation is not required, and the description covers data range and change reporting. The one gap is the absence of routing guidance among the four sibling pricing tools, which an agent would need in order to choose 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%, so both parameters (model, response_format) are already documented in the schema, including an example model id and enum values. The description only reinforces 'one model' per call and adds no format or syntax detail beyond the schema, so the baseline 3 applies.

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 (retrieves price history) and resource (one model's pricing) with scope qualifiers: monthly granularity, since the model appeared on OpenRouter, plus today's price. An agent can distinguish this from siblings like price_changes or estimate_cost, which do not cover a single model's full historical timeline.

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?

No explicit when-to-use or when-not-to-use guidance is given, and no sibling tool is named as an alternative. The existence of a sibling named price_changes makes the omission notable, since the agent must guess which tool covers change history versus general price history.

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