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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real value beyond that by clarifying the return contract (a URL to view elsewhere, not the stats themselves), which prevents a wrong follow-up call. It says nothing about failure modes, e.g. what happens when the identifier has no tracker tag.

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?

Front-loaded with the verb and resource, then a compact enumeration of accepted inputs, then a short clarifying sentence. It is a bit dense in one sentence but every clause carries information; nothing reads as filler.

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, read-only lookup with no output schema, the description supplies the two things the agent needs: what inputs are valid and that the result is a location rather than stats data. Annotations cover safety. Only the error/not-found behavior is left unspecified, which is a minor gap for this tool shape.

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 the single parameter is fully documented, so the baseline is 3. The description's list of accepted identifier types closely mirrors the schema text ("Slug, short URL, page URL, domain, tracker id or tag URL"), adding no format, normalization, or ambiguity-resolution 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 ("Get the stats page URL") and enumerates exactly which kinds of identifiers it accepts (slug, short URL, destination URL, tracker id/tag URL, page URL/domain). The second sentence reinforces the output semantics: it returns the location of stats, not stats data. It never names or contrasts with the close sibling lookup_url, which accepts overlapping input types (slug/short URL), so the agent must infer when to pick this one.

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?

It clearly frames the usage context ("for anything b59.link tracks") and pre-answers the likely follow-up question by stating stats are viewed on b59.link rather than returned here. There is no explicit when-not guidance or comparison to lookup_url / create_tracker, so an agent facing an ambiguous slug input has no rule for choosing between them.

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