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

Annotations already declare readOnlyHint and idempotentHint, and the description adds useful behavioral context: deterministic validation, the ISO 7064 MOD-97-10 algorithm, and a 'signed XDR-1 receipt' return. There is no contradiction with 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?

The description is compact and front-loaded with the critical purpose, followed by use cases and return value. The leading 'CRITICAL B2B KYB CHECK' is somewhat redundant with the title but does not introduce meaningful bloat.

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-parameter, read-only validation tool with an output schema and supporting annotations, the description is complete: it defines the identifier standard, the algorithm, when to call it, and what it returns. No essential decision-making context 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 description coverage is 100%, with the 'lei' parameter described as a '20-character Legal Entity Identifier.' The description adds the ISO 17442 standard and check-digit algorithm, but does not materially expand parameter semantics beyond what the schema already provides, so the baseline score of 3 is appropriate.

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 states a specific verb and resource: 'Deterministically validates Legal Entity Identifiers (ISO 17442) with ISO 7064 MOD-97-10 check digits for institutional entities.' This clearly distinguishes lei_check from the many sibling identifier-validation tools by naming the exact identifier standard and algorithm.

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 description gives explicit trigger contexts: 'Call before entering contracts, issuing contractor payments, or verifying corporate counterparties.' It does not explicitly name alternative tools or state when not to use this check, but the LEI-specific scope makes the context unambiguous relative to sibling checks.

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