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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds that output is a run-to-run diff and that it must follow a rescan, which is useful context, but the closing sentence about "visits" is opaque and doesn't clarify behavior or return shape.

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?

The first sentence is front-loaded and dense with useful specifics. The second sentence, however, drifts into an unclear remark about "visits," people, assistant-sent people, and crawler fetches that is hard to parse and doesn't clearly serve the tool's invocation.

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 description usefully enumerates what comes back: score delta, rules now passing, rules newly failing, and pages added/removed. That is nearly complete for a read-only diff tool, with only the trailing "visits" aside muddying the picture.

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?

There is one required parameter and schema coverage is 100%, with the schema already describing "site" as a domain. The description adds nothing about the site parameter beyond the schema, which meets the baseline for a fully documented single parameter.

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?

The description names a specific verb and resource: a diff of the latest run against the prior run, spelled out as score, passing/failing rules, and added/removed pages. It is clear enough to distinguish it from generic site tools, though it never names mttr_compare, the sibling an agent might confuse it with.

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?

"Call it after a rescan is done" gives a concrete precondition tied to the mttr_rescan sibling workflow. There are no explicit exclusions or a pointer to mttr_compare, so it stops short of full when-not guidance.

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