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

Annotations already declare readOnly/idempotent/non-destructive/open-world, so safety is covered; the description adds genuinely new behavior: execution happens through a specific third-party Actor (skilled_glee/contact-details-extractor) on the caller's own Apify account, with pay-per-event billing. It also discloses a real limitation (North American phone numbers only), which prevents over-broad expectations.

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?

Two dense sentences with zero filler: extraction scope first, execution and cost second. Nothing repeats the title or schema.

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 two-parameter, read-only tool with full schema coverage, the description covers what is extracted and the billing/account model. It does not say whether results are returned per-URL or aggregated, nor how partial failures are reported, and there is no output schema to fall back on — a minor but real gap.

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%, so pageUrls (1-25 URIs) and the optional apify_token fallback are already documented; the description adds no syntax, batching, or per-URL semantics beyond what the schema says. Baseline 3 applies since the schema carries the parameter burden.

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 (extract) and a precisely enumerated resource set (emails incl. mailto, North American phone numbers, LinkedIn/X/Facebook/Instagram/YouTube links, contact/about/team page links) from web pages. That enumeration cleanly separates it from siblings like extract_article, extract_web_metadata and extract_website_content without needing to name them.

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?

Usage is only implied by the resource list; there is no explicit when-to-use/when-not or pointer to alternatives such as extract_website_content for broader scraping or verify_emails for validation. The billing note ($0.0015/page, charged to the user's own Apify account) is a useful cost signal that helps an agent decide, but it is not routing guidance.

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