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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safe-read profile is covered. The description adds the concrete payload shape (storage, defaultDomain, catalogs with tracking tags, marketplaces[]), which is real added context, but it says nothing about failure modes, error output, or auth/rate-limit behavior for a health probe.

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 compact sentences front-load the purpose, then the return shape, then the usage directive. No sentence is wasted, and even the OpenAPI reference is a single short tag rather than prose.

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 no input parameters and no output schema, the description correctly compensates by enumerating the returned fields, so an agent knows what it gets back without a schema. The only gap is that error/failure behavior for a health check is unstated.

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 and the schema is empty, so there is nothing for the description to disambiguate; baseline 4 applies. The defaultDomain value (amazon.se) is inlined as useful context rather than parameter guidance.

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+resource ('Health check for Birthday Gift Finder') and enumerates what it returns (ok, storage, defaultDomain, catalogs, marketplaces[]), which is far more than the title 'Health & marketplaces' conveys. It is distinguishable from siblings like get_catalog and list_marketplaces because it is framed as a service-level health probe, though it never explicitly says it is not those tools.

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 this first' is an explicit usage directive that tells an agent when to reach for this tool relative to all others, which is unusually strong guidance. It stops short of 5 because there is no explicit when-not or named alternative for the marketplace/catalog data that list_marketplaces and get_catalog also surface.

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