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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower; the description still adds real value by disclosing that records are limited to nonzero published entries, bounded to a hot window, and that omitted dates are not zero-filled. The 'do not sum as daily flow' caveat is a genuinely useful interpretive warning. It stops short of describing pagination mechanics or response size.

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 purpose, then contents, then usage examples and a caveat. Every sentence contributes; the content-list sentence is slightly dense but earns its place given there is no output schema.

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 enumerating what comes back (settlement dates, quantities, SEC price fields, source-row counts, pagination, provenance) and by flagging the nonzero-only and no-zero-fill behaviors. Combined with annotations that carry the safety profile, an agent has enough to call it correctly, though pagination behavior across pages is left implicit.

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 all six parameters (limit, offset, symbol, start_date, end_date, response_format) are already documented in the schema. The description only implies their existence via 'bounded, paginated' and 'settlement dates', adding no format or default detail beyond the schema. Baseline 3 applies.

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 precise verb and resource — a bounded, paginated history of published nonzero SEC fails-to-deliver balance records for one ticker — and scopes it to the self-hosted hot window. This cleanly separates it from siblings like sec_ftd_latest (single point), sec_ftd_top (ranked aggregation), and sec_ftd_compare.

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 concrete use-case phrasing ('show GME FTD balances over time', 'chart TSLA published fail balances this quarter', inspect point-in-time changes) that pins down the intended scenario. It does not explicitly name when to prefer a sibling such as sec_ftd_latest or sec_ftd_top instead, so it falls short of full alternative routing.

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