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

With annotations covering read-only and open-world behavior, the description goes further: it explains the output shape (hash, changed true/false, word count, fetch time), the previous_hash null convention, text normalization, and detailed payment/failure semantics for both x402 and pack-credit paths. This is exactly the extra context an agent needs beyond the 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?

Front-loaded with the core action and output shape in the first two sentences, followed by use cases and payment terms. The payment paragraph is long but earns its place because billing and refund behavior are not available elsewhere. Minor trimming could still improve it.

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?

There is no output schema, and the description fully explains the return values (sha256 hash, changed boolean, word count, fetch time). It also covers the first-call null convention, normalization behavior, and billing/failure outcomes. Nothing an agent needs to call this correctly is 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%, so the baseline is 3. The description adds real meaning: previous_hash must come from a prior call and should be null on the first check, and the change flag is computed against that value. It also reinforces the URL must be public, but most parameter documentation is already in the schema.

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: detects whether a web page changed since last check, fetches a public URL, normalizes main text, returns sha256 hash. It distinguishes itself from a monitoring subscription service ("no webhooks or stored subscriptions"), but does not explicitly differentiate from sibling tools like url_probe or page_extract.

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?

Clear context for when to use: a one-shot change check against a previous hash, for price/policy/docs pages. It rules out webhooks and stored subscriptions, but does not name when an agent should pick url_probe or page_extract instead. No explicit exclusions beyond the one-shot nature.

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