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 the service footprint (50 states + DC) and the returned fields, but omits the behavior that matters for a 'check' tool — what happens for an unsupported zip (false result vs. error) and whether a bare 5-digit input is normalized.

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 short sentences, zero filler, with the primary capability front-loaded and the return values appended after. Nothing restates the title verbatim enough to be wasted.

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 one-parameter read-only lookup with full schema coverage and no output schema, the description covers purpose, scope, and return fields, which is nearly enough. The only real gap is the failure/negative-result case, which an agent would need in order to branch on the outcome.

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% and the single parameter is documented as a '5-digit zip code', so the baseline would be 3. The description adds real meaning beyond that by restricting input to US zips in the 50 states and DC, which the schema never states.

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 ('Checks whether Lokuli can call pros near a US zip code') plus a geographic scope (50 states and DC), so an agent can tell it is a coverage lookup rather than a business search or a booking. It does not explicitly name a sibling to contrast with, which keeps it below 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?

Usage is only implied: an agent can infer this is a pre-flight eligibility check before find_businesses or book_appointment, but the description never says when to call it, whether it is a prerequisite, or what to do instead when the zip is not served.

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