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

Annotations already establish readOnly, idempotent, non-destructive, closed-world behavior, so the baseline is satisfied without effort. The description adds genuine context beyond them: exactly what the result contains (rate ranges plus suggested daily/hourly price), that a listing link to Parksy is included, and the important framing that the figure is an estimate rather than a quote or guarantee. It does not cover failure behavior for an unresolvable place, which keeps it off a 5.

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?

The payload description is front-loaded with the outcome and the returned figures, then the usage trigger, then the caveat — a sensible order with no filler sentences. Minor redundancy from repeating the country-disambiguation hint already present in the schema keeps it from a 5.

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 five optional parameters, no output schema, and safety already carried by annotations, the description does the remaining work: it explains the shape of the return (rate ranges, suggested price, listing link) and sets expectations that values are estimates. An agent has enough to select and call it correctly; only edge-case behavior (unknown place, ambiguous location returns) is left unaddressed.

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 each parameter carries its own explanation (place formats, two-letter country code, optional postcode, indoor/outdoor enum, secure_access meaning). The description's only parameter-adjacent advice, adding the country for common place names, largely restates what the `place` schema field already says. Baseline 3 is correct.

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 names a specific verb and resource ("Estimates what a parking provider could charge for a parking space") and even enumerates the returned figures (monthly/weekly range, suggested daily and hourly price) plus a link to list on Parksy. That is far more specific than any sibling (search_parking, get_listing, parking_guides), though it never explicitly contrasts itself with them.

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?

It gives a concrete trigger phrase set: "Use this when someone asks what a garage, driveway or parking space is worth, could earn or should charge." It also adds an input-shaping rule ("Add the country when a place name is common") and a scope caveat ("An estimate only"). No explicit when-not-use or named alternative is provided, so it stops short of a 5.

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