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

Beyond the readOnly/idempotent annotations, the description discloses important behaviors: multi-endpoint cascading lookups, graceful degradation when GLEIF/OpenFIGI are down, explicit `unresolved` reporting, and the `figi_candidates` behavior when a name matches multiple instruments. It also explains edge cases like non-equity instruments and ISIN-to-LEI resolution, giving the agent a realistic model of the tool's behavior.

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 long, but the length is justified by the tool's multi-type, multi-source complexity. It is front-loaded with use cases, organized by entity type, and the critical caveats are placed inline where they are relevant. A slightly tighter edit could reduce repetition, but the structure earns its length.

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 tool with no output schema and complex multi-source resolution behavior, the description is remarkably complete: it covers the identifier sets, the source labels, the unresolved behavior, multi-match handling, fallback degradation, and the mapping from an ISIN to a legal entity. An agent has enough to invoke it correctly and anticipate the shape of its results.

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?

Although the schema already covers both parameters at 100%, the description adds substantial meaning: accepted input forms for company (ticker, CIK, ISIN, name) and drug (brand or generic), the exact formatting warning for bonds, and a concrete instruction to pass only the entity name, not the full noun phrase. This goes well beyond the schema's generic descriptions.

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 concrete trigger phrases and defines the core action: resolving a user-spoken name to the canonical identifiers other tools require. It names the supported entity types (company, drug) and the identifier families returned, making the tool's role unmistakable and distinct from siblings like entity_profile or compare_entities.

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 usage direction: 'Use FIRST whenever you have a name but need an ID,' and enumerates many example queries that signal the right moment to call it. It does not explicitly state when NOT to use it or compare it to sibling tools, but the positive guidance is strong and clear.

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