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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint, so the safety profile is covered. The description adds real value beyond them: it discloses a 10-credit cost, states that findings are tallied and deduplicated into unique records, and scopes extraction to 'public' contact data. It does not cover failure modes (JS-rendered pages, blocked sites) or pagination/truncation behavior.

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?

Three short sentences, front-loaded with the action and resource, with the cost noted parenthetically at the end. Minor waste: the title is repeated twice at the start ('Contact Extractor: Contact Extractor scrapes...'), which adds no information.

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 an output schema present, return-shape explanation is unnecessary, and the description covers purpose, cost, and deduplication. For an open-world scraping tool it is largely complete, though it omits any note on coverage limits or pages that cannot be scraped.

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%, including the -1 unlimited semantics for limit, so the schema already does the parameter work. The description adds no format details, URL constraints, or explanation of how limit interacts with the deduplication tally, so the baseline 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 states a specific verb (scrapes) and concrete resources (public email addresses, phone numbers, physical addresses) against a named input (any web page URL), which clearly separates it from siblings like EmailValidator or LinkScraper. It does not explicitly name a sibling it should be preferred over, so it stops short of a 5.

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 or when-not guidance and no mention of alternatives. The only implied usage cue is 'any web page URL', leaving the agent to infer that this is for page-level contact harvesting rather than validation or enrichment.

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