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

With no annotations, the description carries the full burden, and it does well: it discloses the return contents (registered/listable status, registration wording, how it was resolved) and the fallback path when no match is found. The closing 'Never a guess' sets expectations about abstention rather than fabrication. It stops short of stating permissions, rate limits, or whether the lookup is read-only, which keeps it from a 5.

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?

Three short sentences, front-loaded with the core action and input forms, followed by return shape and the no-match fallback. Every clause carries information; nothing is padding.

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 one-parameter lookup with no output schema and no annotations, the description covers inputs, outputs, resolution explanation, and the no-match behavior. The main remaining gap is sibling disambiguation against providers_search and providers_get.

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 coverage is 100% and the single 'query' parameter is already documented as 'A provider name, website URL, or postcode'. The description restates those same three accepted forms without adding format rules, normalization behavior, or examples, so the schema does the real work. Baseline 3 applies.

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 ('Check a provider ... against our CQC/GPhC register data') and names the accepted input forms. It is clear what the tool does, but it does not distinguish itself from the closely named siblings providers_search and providers_get, leaving the agent to guess which of the three to use.

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?

There is no explicit statement of when to use this tool over providers_search or providers_get, nor any prerequisites. The only routing-like sentence ('If we don't hold it, returns the official register to search by hand') describes fallback behavior of the result, not when to select this tool, so usage is only weakly implied.

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