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

Adds substantial context beyond the annotations: 404-on-no-match with no charge, CC0 public-domain licensing, and a $0.003 USDC-on-Base cost via x402. The pricing and error behavior are exactly the kind of traits annotations don't convey. It doesn't explain the payment side effect behind readOnlyHint=false, but nothing is contradicted.

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 core purpose and return fields, then adds cost/error/usage in short sentences. The long field enumeration is dense but each item earns its place by telling the agent what it will receive; slightly over-stuffed.

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 lookup tool with no output schema, the description fully covers what fields are returned, the licensing, the error path (404, uncharged), and the payment mechanism. An agent has everything needed to call it correctly and interpret the result.

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 (id and name) are already fully documented in the schema. The description restates 'by name or Wikidata ID' but adds no syntax, format, or precedence detail beyond what the schema provides, so the baseline 3 applies.

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/resource ('Facts about a company') and enumerates the exact fields returned (website, founding date, country, HQ, industries, CEO, founders, parent, employee count, tickers, LEI, Wikidata/Wikipedia links), making it clearly distinct from siblings like wikipedia, country, or coin.

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?

'Use to enrich leads, vendors and counterparties or ground an answer about a company' gives concrete use cases, and 'best for established and listed companies' implies the when-not condition (obscure companies may 404). It does not name an alternative sibling (e.g. wikipedia) for cases where this tool has no match, so it stops short of a full 5.

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