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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered structurally. The description adds useful context by naming the response fields, but says nothing about auth/key requirements, rate limits, or behavior on an unknown CUI.

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?

One compact sentence listing the return payload plus a single worked example; the highest-value information (what you get back) is front-loaded. The example is slightly redundant with the schema's own examples array, keeping it out of the top band.

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 output schema, the description helpfully enumerates the return fields, which is exactly what is needed to judge whether to call it. A note on what happens for an invalid/unknown CUI is the only notable omission for a two-parameter read tool whose annotations cover safety.

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% (both cui and _apiKey are documented in the schema), so the baseline of 3 applies. The description repeats the CUI parameter in prose and in an example but adds no format, range, or constraint detail 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+resource ('Concept detail for a CUI') and enumerates the returned fields (preferred name, semantic types, atom count, relation count), which lets an agent place it against umls_search/umls_atoms/umls_crosswalk. It does not explicitly name those siblings, so the differentiation is inferential rather than stated.

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?

The example implies the intended usage (look up a known CUI), and the returned fields imply a detail-fetch role versus a search tool. However, there is no explicit statement of when to use this over umls_search or umls_atoms, and no mention of prerequisites such as needing a valid CUI.

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