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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuine value by naming the fields that come back (category, location, website, admission, contactInfo, source, commercial), which no output schema provides, but says nothing about not-found behavior or site scoping.

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 front-loaded sentence with no filler; the field list is terse but every token carries information. The trailing enumeration is slightly list-like but appropriate given there is no output schema.

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 two-parameter read-only getter whose annotations cover safety and whose schema fully documents both inputs, the description supplies the one missing piece: what the response looks like. Nothing essential to invoking it correctly is absent.

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% and both parameters carry descriptions pointing to list_sites and list_activities as sources of the values, so the schema does the heavy lifting. The description adds no additional meaning about siteSlug or activityId.

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 ("Returns one activity") and enumerates the returned fields, which is far more specific than the title's restatement. It implicitly separates itself from list_activities by saying "one activity", but never names that sibling explicitly.

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?

There is no when-to-use guidance, no mention of the list_activities alternative, and no statement of what happens when the activity does not exist or the slug is wrong. The only cue is the word "one", leaving the agent to infer this is a single-record lookup by id.

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