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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new context the annotations cannot: it is free, requires no API key, and uncovered counties incur no credit charge — the cost/auth facts an agent needs before planning a sequence.

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 short sentences, zero padding, with the cost/auth qualifier front-loaded and the mode switch stated before the credit caveat. Nothing restates the title or the annotations.

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 2-parameter read-only tool with full schema coverage and rich annotations, the description covers both output modes, cost, and auth. The one gap is that with no output schema it never says what the response shape looks like (boolean vs list of counties), leaving the agent to infer the format.

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 would be 3. The description goes beyond it by defining the behavioral meaning of omitting county — the tool switches from a single-county boolean check to enumerating all covered counties in the state — which the schema's 'Optional county name' text does not convey.

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 and covers both operating modes explicitly: it 'says whether a county is in the current data release' or 'lists every covered county in a state when no county is given'. The distinction from the find_parcels_* siblings is obvious from the resource named (coverage, not parcels).

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?

'Free, no API key' plus the credit note give practical context for deciding to call it, and the no-county case is described. However, no sibling is named as an alternative and there is no explicit instruction such as 'call this before find_parcels_by_apn to confirm the county is covered', so the when-to-use logic is only implied.

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