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

The readOnlyHint annotation already establishes this as a safe, non-mutating read. The description adds the underlying API endpoint mapping, which aids traceability, but says nothing about failure behavior (e.g., unknown/404 IDs) or response characteristics beyond what the annotation already covers.

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 sentences, front-loaded with the action and resource, followed by the endpoint reference. Nothing is redundant or padded.

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 trivial single-parameter read tool with full schema coverage and a readOnlyHint, the description is nearly sufficient. The only gap is the absence of an output shape hint, and since no output schema exists, a brief note on the returned facility object would have fully closed the loop.

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% for the single 'id' parameter, so the schema already explains it as 'The Metriport Facility ID.' The description restates the same idea ('by its Metriport ID') without adding format, source, or lookup guidance, so the baseline of 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 ('Get a single Facility') and adds the HTTP route, which makes the intent unambiguous. The word 'single' implicitly contrasts with the sibling metriport_list_facilities, but no sibling is named, so differentiation is inferred rather than explicit.

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?

'by its Metriport ID' implies the caller must already have an ID, which is a reasonable usage cue, and the single-vs-list framing hints at when to prefer this over metriport_list_facilities. However, there is no explicit when-to-use statement or guidance on what to do when 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.