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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the bar is lower. The description still adds real value beyond them: it defines what a fail-to-deliver is and relays the SEC's caveat that FTDs are NOT evidence of naked short selling, which prevents an agent from misinterpreting the output. It does not mention rate limits, freshness/coverage limits, or error 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 verb+resource lead is front-loaded in the first clause, followed by the return fields and then the interpretive caveat and example queries. Despite being multi-sentence, every sentence carries load — domain definition, output shape, correct interpretation, and routing examples — with 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?

With no output schema, the description compensates by enumerating the returned fields, and it supplies the semantic grounding (what an FTD is, the SEC disclaimer) an agent needs to answer and interpret correctly. Nothing essential for a read-only data lookup is missing.

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 both parameters (symbol, periods) are already fully documented in the schema, including the 1-6 range and 'one file per half month' semantics. The description adds nothing further about parameter meaning, so the 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 specific verb and resource — fails-to-deliver history for one US-listed security — and enumerates the returned fields (settlement date, shares, closing price, description, CUSIP). Scope is clearly single-security-by-ticker, which implicitly separates it from the broader ftd_largest and ftd_periods siblings, but neither sibling is named explicitly, so the differentiation is left to inference.

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?

Provides concrete usage scenarios via example questions ('what were the fails-to-deliver for GME', 'has this stock had settlement failures recently'), giving an agent clear context for when to reach for this tool. However, it names no alternatives and gives no exclusions, so routing versus ftd_largest / ftd_periods must be inferred.

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