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

Annotations already declare readOnlyHint=true, and the description adds nothing beyond that — no note on 404 behavior for a missing id, no auth/permission requirements, no rate-limit or subdomain fallback behavior. The 'GET /patients/{id}' line is a restatement of the HTTP shape rather than new behavioral context.

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 short, front-loaded sentences with no padding. The second sentence largely echoes the tool name and title, which slightly limits its value but keeps it tight.

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 simple single-record fetch with readOnlyHint covering the safety profile, this is minimally adequate. With no output schema, the description could usefully say what a patient record contains, but the omission is not severe for a lookup tool.

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 both the id path param and the subdomain fallback are already documented in the schema. The description's 'by id' adds no syntax or format detail beyond that, making the baseline 3 correct.

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 ('Fetch a single patient by id') and pins down the scope as a single-record lookup, which meaningfully separates it from nexhealth_search_patients and nexhealth_list_* siblings. It does not name any sibling explicitly, so it stops short of a 5.

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?

Only the phrase 'by id' hints at when this is appropriate versus nexhealth_search_patients. There is no explicit statement of when to use this tool, when not to, or what to do if the id is unknown.

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