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

Goes well beyond the annotations by disclosing the billing model (pay-per-event $0.0004/URL, billed by Apify) and that it runs on the caller's own Apify account — material facts an agent cannot get from readOnlyHint/idempotentHint. It also notes the fallback apify_token path for clients that can't send auth headers.

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: capability and return fields first, the body-read exclusion second, cost/account third. No padding, and the most decision-relevant information is front-loaded.

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?

Without an output schema, the description does the work of explaining return fields, and the annotations already cover safety. What's missing is failure semantics (what happens on timeouts, DNS errors, or non-2xx) and the 25-URL batch limit, which matter for a network probe.

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?

With only 40% schema description coverage, the description does fill some gaps by implying method (HEAD vs GET) and redirect handling, but it never mentions the 25-URL cap, the timeoutSecs/timeout behavior, or the semantics of followRedirects=false. Two documented parameters plus visible enum/defaults carry most of the weight.

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 (probe/check URLs) and enumerates exactly what is returned: HTTP status, final URL after redirects, redirect count, Content-Type, timing. The sentence 'No page body is read' cleanly separates it from the sibling extract_* tools that fetch content.

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 scope statement implies when this is the right pick (link validation, redirect/header inspection rather than content extraction), but no sibling is named and there is no explicit 'use X instead when...' guidance. The agent must infer the boundary from the phrase 'No page body is read.'

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