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

Annotations already declare readOnlyHint, idempotentHint, and closed-world behavior, so safety needs no restating. The description adds real behavioral context the annotations cannot: counts span all listings with a sourced matching service, include later additions to homepage-screened records, and services reflect scope rather than quality. That last caveat materially affects how an agent interprets the numbers.

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 what is returned, followed by the caveat. No filler. It loses a point because phrases like 'sourced matching service' and 'homepage-screened records' are internal jargon that assumes context the agent may not have.

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 zero-parameter read with annotation coverage, the explanation is nearly sufficient: it says values plus counts are returned. Because there is no output schema, a brief note on the response shape (e.g. service label alongside count) would have made it complete.

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?

This tool takes zero parameters, so there is no parameter meaning to add; the baseline applies. Nothing in the description conflicts with the empty object 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 identifies the resource precisely: the service filter values that search_firms accepts, plus counts. It ties itself to the sibling that consumes the output, which helps an agent tell it apart from list_places. It never states an explicit verb ('lists'/'returns') and is phrased as a noun fragment, which keeps it short of a 5.

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?

By naming search_firms as the consumer, the description implies the use case: call this to discover valid service filter values before searching. There is no explicit when-to-use, no when-not-to-use, and no statement of whether other siblings (e.g. list_places) offer overlapping enumerations.

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