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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely useful non-safety context: each entry carries a row count and a public download URL, and the tool does not fetch/unpack the archives. It stops short of describing page ordering or error behavior beyond 'most-recent first' implied by the limit param.

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?

Front-loads what the tool returns before the comparative guidance with the sibling. Dense but each clause earns its place; the parenthetical explanations are compact rather than redundant. Slightly long single sentence but no 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?

No output schema exists, so the description must convey the return shape — and it does (per-file row count plus public CSV-in-zip download URL). Combined with the granularity routing and the sibling comparison, an agent has everything needed to call it 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 coverage is 100% and enum values are already documented, so the baseline is 3. The description reinforces the granularity meaning (5-minute rolling 'slice' files vs. one-per-prior-day 'cumulative' files) but adds no syntax or format detail for limit/regulator/asset_class beyond 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?

Opens with a specific verb (Index) and resource (DTCC's public swap dissemination data files), scoped by regulator/asset-class. It distinguishes the two file families (intraday slices vs. end-of-day cumulative) and clearly separates itself from the sibling dtcc_swaps_recent.

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?

Explicitly states the selection condition — use it to find bulk files covering more history than dtcc_swaps_recent's rolling ~100-row live window — and names the boundary ('it lists the files, it does not download/unzip them'). An agent knows exactly when this tool applies and when it does not.

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