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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuine operational context — no API key required, an optional key raises rate limits, and the data source is Bloomberg OpenFIGI — but it labels an external third-party API call while annotations set openWorldHint=false, a tension worth noting even if not a hard contradiction.

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-loaded with the core purpose, then usage bullets, then idType reference, then a practical exchCode tip and source note. Every block is scannable and none is wasted, though the idType bullet list partially duplicates the schema's mappings description.

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?

Covers purpose, when-to-use, accepted ID systems, exchange targeting, and rate-limit/auth expectations; an output schema exists so return values need not be described. The notable omission is that the description never mentions batching semantics of the 'mappings' list or acknowledges the unrelated-looking extra parameters bundled in the schema.

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 idType enumeration and ISIN/CUSIP examples largely restate the 'mappings' field's own schema description, but the 'Include exchCode: US to target US exchanges for ticker lookups' tip adds real meaning the schema lacks. The remaining nested fields (wholesaler_ids, exclude_fillers, source_resource_id, mcp_prompt_id, question_asked) are never mentioned despite appearing in the schema and looking unrelated to ID mapping.

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 and resource ('Map financial instrument identifiers ... Converts between ticker symbols, ISINs, CUSIPs, and FIGIs') and names the underlying service, so the agent can distinguish it from lookup/search siblings. It does not explicitly contrast itself with siblings like SearchFigiInstruments or LookupTicker, so it stops short of a 5.

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?

Provides a concrete 'Use this tool when:' list with three real scenarios (ticker→ISIN/CUSIP, normalizing IDs across EDGAR/Yahoo sources, finding the exchange). That is clear positive guidance, but there is no when-not condition and no named alternative tool to route to.

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