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 still adds value beyond them: 'Not paginated', the special bucket semantics for no_connection_declared / no_payment_declared, and 'Free, no payment or account required' — none of which appear in the 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?

Dense but front-loaded: what it counts first, then when to use it, then behavioral notes. The dimension list is long but each item is load-bearing; a slightly run-on first sentence keeps it just short of ideal.

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 14-parameter, zero-required, non-paginated aggregation tool with no output schema, the description covers purpose, filter parity with search_listings, pagination behavior, and cost/auth requirements. The only gap is that the returned count shape (per-dimension buckets) is only implied rather than stated.

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%, so the baseline is 3. The description adds meaning the schema does not: it enumerates which dimensions are faceted and explains the special 'none' buckets (no_connection_declared / no_payment_declared), which are not present in the schema's enum lists.

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?

Names a specific verb ('Counts of matching listings') plus the exact facet dimensions it groups by (task_category, listing_type, payment network, import source, connection type, payment type), and ties its filter set to search_listings (including q). An agent can immediately tell this apart from search_listings: same filters, aggregated counts instead of listing rows.

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?

'Use it to see what exists before narrowing a search' gives a concrete when-to-use and implicitly routes the agent to search_listings for the actual result set. It lacks an explicit when-not-to-use or a named alternative clause, but the pairing with search_listings is clear.

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