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

Annotations already declare readOnlyHint and idempotentHint, but the description adds substantial behavioral context: it returns figi_candidates when multiple matches exist, explicitly lists unresolved identifiers, degrades gracefully when GLEIF/OpenFIGI are unavailable, cascades through multiple lookup endpoints internally, and handles non-US issuers via ISIN-to-LEI mapping. This rich disclosure goes well beyond what annotations provide.

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 extensive but well-organized, starting with the tool's purpose and usage-first directive. Each sentence adds specific technical or behavioral detail, but the length is substantial and includes minor editorial asides (e.g., 'which is the correct answer...'). It is appropriately dense for a complex tool, but not perfectly concise.

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?

Given the tool's complexity, two parameters, and no output schema, the description is exceptionally complete. It covers all input types, output behaviors (including figi_candidates and unresolved), error/degradation modes, and the relationship between identifiers. An agent has everything it needs to correctly select and call this tool, including edge cases.

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 description coverage is 100%, the tool description adds meaningful parameter semantics: it gives concrete examples (AAPL, 0000320193, ozempic), explains the 'only entity name' rule for bonds (e.g., drop trailing security-class words), and clarifies that value can be an ISIN for company type. This guidance is essential for correct invocation and not present in 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 states a specific verb and resource: resolve a user-spoken name to canonical/official identifiers. It clearly distinguishes itself from siblings by explaining that it maps names to IDs needed by other tools, and lists concrete supported types (company, drug) with their identifier sets. It goes beyond a generic 'resolve entity' title by detailing the cross-source identity spine, making it unmistakable.

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 says 'Use FIRST whenever you have a name but need an ID,' giving a clear condition for when to invoke this tool. It also provides domain-specific guidance, such as how to pass bond issuer names and what happens with non-equity instruments. However, it does not explicitly mention alternative tools or when not to use this tool (beyond implying that if you already have an ID, you don't need it), so it stops short of a perfect 5.

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