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

Annotations already establish read-only, idempotent, non-destructive behavior; the description adds valuable context beyond that: the SEC 13F source, OpenFIGI-based ticker resolution rather than a bulk symbol table, and the amendment handling rule. This gives the agent meaningful expectations beyond the structured hints.

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 compact and front-loads the core purpose before details. Each sentence earns its place: input forms, return fields, query examples, data source, and an edge-case caveat. It is slightly dense but avoids repetition or filler.

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 read-only lookup with schema-covered parameters and safety annotations, the description covers everything an agent needs: input formats, return fields, ranking basis, source, and the amended-filing counting behavior. No output schema exists, so the explicit listing of returned fields is especially valuable and complete.

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?

Schema coverage is 100% and both parameters are already documented clearly. The description still adds value by specifying accepted security identifiers (company name, ticker, 9-character CUSIP), clarifying that tickers are resolved via OpenFIGI, and confirming the security parameter semantics with examples.

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 action and resource: identifying which institutional managers hold a given US-listed security, ranked by position size. It clearly differentiates this from manager-first 13F APIs and includes concrete natural-language examples that leave no ambiguity about the tool's function.

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 frames this as the reverse of manager-first 13F tools, which tells an agent this is the security-first query path. It does not name a specific sibling like manager_portfolio as the alternative, but the 'reverse of every 13F API' guidance provides a clear when-to-use heuristic.

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