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

With no annotations, the description carries the full burden. It discloses that this is a paid tool requiring a two-step payment process (obtain terms, sign, resubmit) and mentions the free pricing alternative. This is critical behavioral context. It does not mention rate limits or failure modes, but for a simple tool this is sufficient.

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?

Two sentences, front-loaded with purpose, then payment instructions, and a pointer to a free alternative. Every sentence earns its place, no fluff.

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?

The tool has no output schema, so the description should hint at return values—it does ('who owns it, position sizes, and changes'). It also explains the payment workflow thoroughly. It could more explicitly state that the second call returns the data, but the implication is clear. Overall complete for the tool's complexity.

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%: both cusip and x_payment are documented in the schema. The description reiterates the payment flow but adds no new parameter semantics beyond what the schema already explains (e.g., the x_payment base64 payload and the two-step process). Baseline 3 is appropriate.

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?

Description clearly states the tool provides institutional holders of a security by CUSIP, including who owns it, position sizes, and changes. This distinguishes it from siblings like manager_holdings (likely about a manager's holdings) and holdings_changes (likely about changes). The title 'Who holds a security (13F)' reinforces the purpose.

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 explains the payment workflow (call without x_payment to get terms, sign, call again with x_payment) and points to the free pricing tool as an alternative for pricing. However, it does not explicitly differentiate when to use security_holders versus holdings_changes or manager_holdings, though the purpose is clear enough to infer.

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