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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is fully covered without the description. The description adds only the concrete id format; it says nothing about not-found behavior or what happens with a malformed id.

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 with no padding; the resource is named before the key. It is efficient, though it is short enough that a clause on failure behavior could have been added at little cost.

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, fully documented, annotated read tool this is close to sufficient, and the singular 'One ... outlet' clarifies the cardinality of the result despite there being no output schema. Missing is any statement of what a miss returns or how errors surface.

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%, so the baseline is 3, and the description earns an extra point by supplying a concrete id example ('us.ca.lib.ca0164-002') that the schema's bare 'Library outlet id' text does not convey. This makes the expected identifier format clear before the call.

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 resource ('One public library outlet') and the lookup key ('by Datamart id'), which distinguishes it from the sibling search tool libraries_search without naming it. It is slightly terse on the verb but the get-by-id semantics are unambiguous.

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?

Offers no explicit when-to-use or when-not guidance and does not point at libraries_search for agents that lack an id. The id example implicitly signals a direct-lookup use case, but the agent must infer that alternative.

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