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

Annotations already declare readOnly, idempotent and non-open-world, so the safety profile is covered. The description adds two pieces of context not in the structured fields: 'Live' (real-time freshness of the readings) and 'Free' (no quota/cost), which is genuinely useful for deciding whether to poll it.

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?

A single front-loaded sentence plus a one-word qualifier. The scope ('every marketplace') and the payload are stated first, with zero filler.

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 no-parameter, read-only status endpoint with no output schema, the description conveys the three return dimensions an agent needs. It could state the shape of the per-marketplace result or whether it aggregates, but nothing essential is missing.

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 tool takes zero parameters, so the baseline is 4. There is nothing for the description to disambiguate, and it correctly spends no words on inputs.

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 resource (health, success rate, response time) and an explicit scope (every marketplace), which cleanly separates it from all the listing/sales siblings. It stops short of an explicit verb (e.g., 'returns' or 'checks'), but the deliverable is unambiguous.

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?

No when-to-use guidance, no preconditions, and no alternatives are named. The 'Live' qualifier implies freshness but nothing tells an agent when to reach for this versus the sibling marketplace tools.

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