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

Goes well beyond the annotations (which only declare read-only/idempotent/non-destructive) by disclosing the 200000-character cap, linear-time complexity, the x402 payment requirement, exact cost per network ($0.01 USDC on Base mainnet, $0.001 on Base Sepolia), and that failed calls are not charged. Cost and payment mechanics are exactly the kind of context an agent cannot infer from structured fields.

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-loads the extracted entity list, then tacks on limits and pricing; every clause carries information. It reads as a single dense run-on sentence, which slightly hurts scannability but wastes no 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?

With no output schema, the entity enumeration effectively communicates what comes back, and limits/cost/payment are covered. It stops short of describing the actual return structure (e.g., grouped by type vs flat list), which is the only meaningful gap for a single-call extraction tool.

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?

Only one parameter, and schema coverage is 100% with maxLength 200000 already documented, so the schema carries the load. The description's 'Input up to 200000 characters' merely restates the schema bound and adds no new syntax or format meaning.

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?

Specific verb (Extracts) plus an exhaustive enumeration of the resource subtypes (emails, URLs, IPv4, EVM addresses, tx hashes, mentions, hashtags, prices, dates, phones). This clearly separates it from text.chunk (splitting) and html.to-text (markup stripping) without needing to open any schema.

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 implied by the entity list, and one useful disambiguation rule is given ('dates, IPs and plain numbers are not reported as phones'), but there is no explicit when-to-use/when-not guidance relative to siblings such as html.to-text or summarize, and no stated prerequisite that input should already be plain text.

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