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

Annotations already cover readOnly/idempotent/openWorld/non-destructive, so the bar is lower; the description still adds real context — it defaults to the latest date in the hosted snapshot, and it enumerates what is returned (exact quantities, issuer labels, SEC price fields, symbol count, provenance). It also pre-empts a common misinterpretation of FTD data. It does not mention rate limits or the size of the hosted window.

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?

Three sentences, front-loaded with the core action and scope, then examples, then the disambiguating negative. Every sentence carries information an agent needs; nothing is padded.

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?

With no output schema, the description compensates by listing the returned fields, and annotations carry the safety profile. The only gap is that it says nothing about ranking criteria or how the default limit affects the result set, which is minor given the schema documents limit.

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% so the baseline is 3, but the description adds meaning beyond the schema by explaining that settlement_date defaults to the latest date in the hosted snapshot, clarifying the otherwise vague 'hosted hot window' wording. The limit and response_format parameters are left entirely to 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?

States a specific verb (rank) plus a precisely scoped resource (largest ticker-level aggregate fails-to-deliver balances published by the SEC for one settlement date). An agent can distinguish it from sec_ftd_latest, sec_ftd_history, sec_ftd_compare, and sec_ftd_search_securities from the text alone.

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?

Gives explicit example phrasings ('largest SEC fail balances today', 'top FTD securities on 2026-08-14') and a use case (market-structure screen), plus a clear exclusion: 'not a misconduct list or short-squeeze signal.' It stops short of naming the sibling tools an agent should use instead for history or comparison, so routing is implied rather than explicit.

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