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

Beyond the annotations (readOnlyHint, openWorldHint, idempotentHint, destructiveHint=false), the description discloses rich behavioral traits: cascading through multiple lookup endpoints, graceful degradation (if GLEIF/OpenFIGI unavailable, EDGAR still returns), handling of ambiguous matches (asserts nothing, returns figi_candidates), explicit unresolved identifier reporting, source label for every identifier, and the ISIN-to-LEI mapping for non-US issuers. This is far more than the annotations provide, giving the agent a clear mental model of how the tool behaves in edge cases.

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 densely packed with actionable information. It front-loads example queries and a directive ('Use FIRST'), then systematically covers supported types, behavior on ambiguity, degradation, and input format. While not terse, every sentence contributes value—examples, caveats, and edge cases—and it is well-organized with clear separations. A bit verbose, but structure prevents it from feeling bloated.

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 high complexity (multiple data sources, two entity types, numerous identifiers, edge cases), the description is exceptionally complete. It covers input formats, output behavior (including unresolved identifiers and figi_candidates), failure modes, source attribution, and even non-obvious cases like non-ticker instruments. It also addresses lifecycle concerns (graceful degradation) and efficiency (replaces 2-3 manual lookups). Nothing an agent needs to call correctly appears 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?

The schema already covers both parameters with descriptions (100% coverage), so the description's additional value is limited but present. For 'value', the description adds critical usage nuance: 'Pass the ENTITY NAME ONLY — for a bond that is the ISSUER exactly as printed... never the question's full noun phrase' and explains why trailing security-class words fail. It also expands on the 'type' enum by detailing what each type returns. This goes beyond the schema's minimal descriptions, earning a 4.

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 user queries ('What's the ticker for…' / 'find the CIK for…') and states a precise verb+resource: resolve a user-spoken NAME to canonical/official identifiers. It clearly distinguishes from siblings by saying 'Use FIRST whenever you have a name but need an ID' and enumerates supported entity types (company, drug) with specific identifier outputs. This leaves no doubt about what the tool does.

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 explicitly tells the agent when to use this tool: 'Use FIRST whenever you have a name but need an ID.' It also provides nuanced guidance on when not to rely on it (e.g., when a name matches multiple instruments it returns candidates rather than asserting, which is correct for ambiguous bond issuers). It implies this is the primary gateway for identifiers, superseding manual lookups, without needing to list every sibling as an alternative.

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