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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, so the safety profile is covered. The description adds genuinely non-obvious context: 'Coverage is not popularity' clarifies a misleading metric, and the affiliate disclosure (purchase_url is a Tallybuy link, commission at no extra cost, must be disclosed) is a behavioral obligation no annotation could carry. The only gap is that coverage is flagged as not-popularity without saying what it actually measures.

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?

Front-loaded with the purpose, then prerequisite ordering, then the two caveats. Every sentence carries distinct information — scope, sequencing, metric semantics, disclosure duty, and sibling routing — with no restatement of the title or 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?

A one-parameter, read-only, openWorldHint=false tool with full annotations and an output schema, so return values need no prose. The description still supplies the two things structured fields can't: the call-first sequencing for a multi-tool workflow and the commission-disclosure requirement.

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?

The single optional 'status' parameter is fully documented in the schema (active/planned/paused), and the description never mentions it — it only notes that status is part of the output. With 100% schema coverage the baseline of 3 applies; the description adds no filtering semantics beyond the 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?

States a specific verb and resource ('List markets') plus the exact payload (status, currencies, published locales, coverage). It closes with a negative scope statement — 'this tool lists no products or prices' — and points to search_products, so an agent can separate it from every sibling without opening a schema.

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?

Explicit sequencing: 'Call it first' because market_id, currency, destination_country and locale come from here — that is the prerequisite for the other five tools. It also names the correct follow-up (search_products) and rules out what this tool does not return, leaving nothing to inference.

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