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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it defaults to the latest settlement date, lists exactly what is returned (quantities, issuer labels, SEC price fields, total count, provenance), and clarifies that it is not a misconduct list or short-squeeze signal. This gives the agent a clear model of the tool's behavior.

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 three sentences with no filler. The action and resource lead the first sentence, followed by output details and default behavior, then usage examples and a caveat. Every sentence earns its place and the structure is front-loaded.

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 three optional parameters and strong safety annotations, the description is complete. It explains the ranking scope, the default date behavior, the exact output components, and provides user-facing example queries. There is no missing information an agent would need to invoke the tool correctly.

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 description coverage is 100%, so the schema already documents all three parameters. The description adds a small but useful note that settlement_date defaults to the latest date in the hosted snapshot, which supplements the schema. No deeper parameter semantics are needed given the simple optional parameters.

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 verb ('Rank') and a precise resource ('largest ticker-level aggregate fails-to-deliver balances published by the SEC for one settlement date'), which clearly defines the tool's scope. It also includes example queries that anchor the intended use, making it easy to distinguish from related FTD tools like sec_ftd_history or sec_ftd_search_securities.

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 provides explicit use cases ('Use this for 'largest SEC fail balances today', 'top FTD securities on 2026-08-14', or a market-structure screen') and a clear when-not ('This is not a misconduct list or short-squeeze signal'). It does not explicitly name alternative sibling tools, but the guidance is concrete enough to route an agent appropriately.

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