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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds only that the result includes vendor and site names, which is mild but genuine extra context; it says nothing about missing-ID/error behavior or permissions.

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?

A single front-loaded sentence that identifies the operation, the lookup key, and the response content with no filler. Every clause earns its place.

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?

No output schema exists, so the description compensates by noting that vendor and site names are included in the result. For a simple one-parameter read tool with full annotation coverage, this is nearly complete, though it omits error behavior for a nonexistent ID.

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% and there is a single required id parameter, so the schema already documents the input fully. The description's 'by ID' adds no format or syntax detail beyond the schema, making the baseline of 3 appropriate.

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 vendor site assignment') and scopes it to lookup 'by ID', which implicitly separates it from the sibling list_vendor_site_assignments. It does not name the sibling explicitly, so it lacks the extra disambiguation that would push it to 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?

The 'by ID' phrasing implies the retrieval use case, but there is no explicit statement of when to use this versus list_vendor_site_assignments or get_vendor. Guidance is only inferable from the name and description, not stated.

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