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

With no annotations, the description carries the full burden and does so well: it declares determinism, states no LLM or network call is made, promises stable JSON output, and discloses the exact cost ($0.001 USDC on Base via x402). It omits failure behavior and the 500k input cap, but the behavioral profile is unusually rich for a tool with zero annotation coverage.

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 tightly packed sentences: capability first, behavioral guarantees second, cost/payment last. Every sentence earns its place and nothing is padded.

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 single-input, no-output-schema tool, the description covers capability, determinism, no external calls, stable output, and payment model. The only real gap is that the JSON output shape is asserted but not described, which is minor since callers typically introspect the actual payload.

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 0% and there is one parameter, so the description technically does not document 'text'. However the parameter name is self-evident and the reserved-baseline for trivial single-parameter tools keeps this at 3; the description adds no format or length guidance (the 500,000 maxLength lives only 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 ('Extract') and resource ('entities from text') and then enumerates the exact entity classes handled (emails, URLs, phone-like numbers, mentions, hashtags, IPv4). This is enough to distinguish it from siblings like extract-article, html-links, and webpage-links without opening 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?

The phrase 'for crawlers and autonomous agent pipelines' implies a usage context, and the determinism note hints at a use case, but there is no explicit when-to-use, when-not-to-use, or named alternative among the many sibling extraction/scraping tools. Usage is inferred rather than stated.

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