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

Annotations already cover the safety profile (read-only, idempotent, closed-world), so the bar is lower, and the description adds real context on top: an API key is required, coverage starts July 2026, values are normalized to USD/RMB per 1M tokens, and source URLs are included. It does not mention pagination or row limits, which is the main remaining gap.

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, front-loaded with the Pro/API-key constraint and the data's scope, then the filter list. Dense and mostly waste-free, though the filter sentence largely restates parameter names already visible in the schema.

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 usefully describes the returned data (daily rows, currency units, source URLs) and the history window, which is what an agent needs to interpret results. It omits pagination and default/maximum limit behavior for a 6-parameter tool with zero required params.

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 50%, so the schema documents model/since/until while vendor, country and limit are bare. The description's 'filter by model, vendor, country and date range' confirms these are filters but adds no format, matching semantics or default behavior beyond what the schema already says, leaving the undocumented half only partly compensated.

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 with unusual precision: daily official list-price history per model, from July 2026, in USD and RMB per 1M tokens, with source URLs. This clearly separates it from a current-price sibling like list_llm_prices, but it never names an alternative, so an agent must infer the split from the word 'history'.

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?

Gives an access precondition ('Pro (API key required)') and enumerates the filter dimensions, which implies how to narrow a query, but it never states when to prefer this over list_llm_prices or list_price_changes, nor any exclusions or rate limits. Usage is implied rather than directed.

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