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

With no annotations provided, the description carries the full burden and does a good job: it discloses the data source (live verified-dealer listings), the metric types (typical, lowest, highest), the currency (GBP), and crucially what the prices are not (trade or valuation estimates). It could add more on freshness or output shape, but the core behavioral traits are transparent.

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, all earning their place: the first states the function and outputs, the second clarifies currency and semantics, and the third gives concrete use cases. It is front-loaded and has no filler.

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-optional-parameter tool with no output schema, the description is complete: it tells the agent what the tool returns, the source of the data, the unit, the optional narrowing behavior, and practical invocation scenarios. Nothing an agent needs to decide whether to call it 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 description coverage is 100%, so the baseline is 3. The description adds 'optionally narrowed to a make or model,' which mirrors the schema rather than adding new semantic depth. It does not explain edge cases like providing only a model, but the schema already documents the parameters adequately.

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 uses a specific verb-resource pair ('Get current UK used-car asking-price guidance') and clearly differentiates from siblings by specifying that it returns typical, lowest, and highest asking prices from live dealer listings, not trade or valuation estimates. This makes it easy for an agent to distinguish from search_used_cars and other sibling tools.

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?

The description gives explicit use cases: answering 'what do X cost used in the UK' and sanity-checking advertised prices. It does not explicitly contrast with sibling tools or state when not to use it, but the intended context is clear enough for an agent to select it.

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