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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description adds genuinely new behavioral context beyond those annotations: quota limits, two payment paths, and the specific MCP metadata key carrying payment. It does not describe error behavior on quota exhaustion, which is the only notable gap.

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 sentences, front-loaded with the capability before the commercial terms, with no filler. The long entity list is dense but functional; the bracketed server note is minor tail noise.

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 an output schema present, return values need no explanation, and the description covers scope, cost, and payment mechanics adequately. The remaining gap is that valid `types` values are not enumerated, leaving an agent to infer them from the prose list.

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 description coverage is 100%, so both parameters are documented structurally, and the description's entity enumeration loosely maps to the `types` filter. However, it does not specify the exact string values or formatting for the comma list, so it adds little meaning beyond what the schema already provides.

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?

The description gives a specific verb ('Pull ... out of') and resource (emails, URLs, EVM addresses, tx hashes, BTC addresses, phones, dates, money, IPs, hashtags, @mentions) with the scope 'any text'. An agent can immediately tell this is a general-purpose entity extractor without opening the 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?

It clearly establishes when the tool applies ('out of any text') and discloses the operational context an agent needs before calling: 10 free calls/day, then paid via x402 or X-API-Key. It does not name sibling tools or exclusions, but the domain is narrow enough that alternatives are not obviously competing.

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