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

Annotations already establish readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds meaningful behavioral context beyond that: the output granularity (daily typical used price and fair range) and access tiers that limit history to 30 days without an API key and 365 days with one.

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 with no waste. The core output is front-loaded, followed by the access constraint, so an agent can parse the key facts immediately.

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?

For a simple two-parameter read-only tool, the description covers what is returned, the granularity, and the tier-based history limits. Annotations and the schema already handle safety and parameter definitions, so nothing essential is missing.

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 100%, so the baseline is 3. The description earns an extra point by clarifying that the 'days' parameter is constrained by access tier: 30 days free, up to 365 days with an API key, which is not stated in 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?

The description states a specific resource and output: daily typical used price and fair range for a model. It is clear what the tool returns but does not explicitly distinguish itself from siblings like get_price or check_price, which likely return current rather than historical pricing.

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?

Usage is implied by the word 'history' and the daily output, but the description never says when to use this tool instead of get_price or check_price. The tier constraints (free 30 days, API key up to 365 days) are useful context, but there are no explicit inclusion or exclusion rules.

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