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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond by enumerating the return shape (host, run, changes, visits, job{id,state,ahead}), the auth requirement ('Needs a key'), and specific failure modes (never-read site or job for another site returns not found). This is unusually complete behavioral disclosure for a read-only tool.

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?

Organized into When/Instead/Inputs/Returns/Fails with the core purpose front-loaded in the first sentence. The telegraphic style is dense but every line carries distinct information; nothing is redundant.

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?

With no output schema, the Returns section fully carries the burden of describing return values, and the Fails section covers error behavior. For a two-parameter read tool, an agent has everything needed to invoke it correctly and interpret the result.

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 already 100%, so the baseline is 3. The description adds real meaning beyond the schema: `site` is a domain like example.com, and `job` is the id returned by clickd_rescan, with the important semantic note that changes stay null until the read is done.

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: 'says what a site's latest read changed against the one before,' then enumerates the change categories (score, rules, pages). It also names the two siblings it is not (clickd_rescan, clickd_site), making disambiguation immediate.

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 'When' line gives an explicit trigger and cadence (after clickd_rescan, poll every minute or two with its job), and the 'Instead' line routes to clickd_rescan for requesting a read and clickd_site for the current report. Both alternatives and the condition selecting them are stated.

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