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

Beyond the provided annotations (readOnly, idempotent, non-destructive), the description adds meaningful nuances: it specifies the GLEIF official mapping source, the output fields, the one-to-many ISIN-to-issuer relationship, and the important distinction between a valid-but-unmapped ISIN and an invalid ISIN. This is valuable behavioral context not captured by 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?

Three sentences, fully front-loaded with the core resolution logic in the first sentence. Each subsequent sentence adds unique value (user intent, edge-case behavior) without repetition or fluff.

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 simple read-only lookup with no output schema, the description fully covers the input format, the output content (LEI, name, jurisdiction, status), the source, and edge cases (unmapped vs invalid). It also signals fidelity to external data ('mapping lags new issuance'), which is important for an open-world 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?

The schema already provides full coverage of the single 'isin' parameter (100% with type, format, and example). The description adds value by giving two concrete examples and clarifying that a structurally valid ISIN may still be unmapped, which enriches the parameter's semantics beyond 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?

The description opens with a specific verb, 'Resolve', and clearly identifies the input (ISIN) and the output (LEI, legal name, jurisdiction, status). It explicitly frames the purpose as answering 'who issued this security', which distinguishes it from sibling tools like bic_to_lei and lei_to_isins by direction and resource.

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 provides clear intended use ('Answers who issued this security') and notes it works for non-US as well as US securities. It does not explicitly name alternatives or when-not-to-use, but the context makes the appropriate use case evident.

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