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

Goes far beyond the annotations (readOnlyHint=false, idempotentHint=false). It discloses the write behavior ("Unlike the other tools this one WRITES: it stores a durable snapshot"), the 6-hour snapshot retention limit, the baselineAt caveat, and the comparable flag semantics including the ruleset-difference scenario. This is exemplary transparency with no contradiction to annotations.

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 description is long but every sentence carries non-obvious, decision-relevant information (write behavior, snapshot rate limiting, baselineAt, comparable flag, ruleset caveat). It is front-loaded with purpose and usage before the caveats. Slightly dense, but the complexity of the tool justifies the length — no wasted words.

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?

Given an output schema exists (covering return values), the description correctly focuses on behavioral semantics rather than return format. It covers write side-effects, snapshot retention policy, baseline ambiguity, and the critical comparable flag pitfall. For a tool with this complexity, nothing important appears missing.

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% — the input schema already fully documents the url parameter, including the bare-domain normalization ("example.com" treated as https://example.com). The description adds no parameter-specific meaning beyond the schema, so the baseline of 3 applies.

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 opens with a specific verb+resource statement: "Re-audit a site and report what moved since it was last checked: which findings are new, which were resolved, and how each category score shifted." It clearly distinguishes from the sibling compare_websites (which compares two sites) by anchoring on comparison against past history rather than another site.

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?

Provides explicit trigger conditions: "Use it after the user says they fixed something, or to verify that a deployment did not regress anything." It also hints at differentiation from "the other tools" by noting this one writes. However, it does not explicitly name alternatives or state when NOT to use it (e.g., when comparing two arbitrary sites, which would be compare_websites).

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