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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds value beyond them by disclosing the cost model ('Flat 5 points per successful run') and the approximate result size (~700 sites), which an agent cannot learn from structured fields.

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 tightly packed sentences: the resource and its fields come first, then the cost note. No filler or restated name/title.

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 one optional parameter, no output schema, and annotations covering behavior, the description is nearly complete — it even lists the returned fields, substituting for a missing output schema. A note on ordering or whether results are paged would close the remaining gap.

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 the single optional 'country' parameter is documented in the schema itself with an example. The description adds no additional semantics about the filter beyond what the schema 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?

The description states a specific resource ('Directory of ~700 Craigslist regional sites') and enumerates the fields returned, which is concrete and non-tautological. It doesn't explicitly distinguish itself from siblings like run_craigslist_categories or run_craigslist_postings_search, though the 'areas' scope is fairly self-evident.

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: the parenthetical 'the alias value for searches' hints that this is a lookup to obtain area values for the postings search tools, but it never says when to call this versus run_craigslist_categories or the postings tools, nor any prerequisites.

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