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 useful behavioral context: the 'hosted hot window', the list of returned fields, and the interpretive caveat that a fail is not evidence of naked short selling.

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 with no filler. The primary action is front-loaded, followed by return-field detail, example queries, and a necessary interpretive caveat. Every sentence earns its place.

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 simple single-ticker lookup with only one required parameter, the description covers the tool's scope, data sources, included fields, and an interpretive caveat. There is no output schema, but the description lists the key return fields. Edge cases like no data or an invalid as_of date are not addressed, but the 'hot window' constraint and schema descriptions mitigate this.

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 baseline is 3. The description reinforces that symbol must be exact and that as_of is a settlement date, but it does not add meaning beyond the schema for any of the three 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 and resource: 'Return the latest published official SEC fails-to-deliver balance for one exact ticker.' It differentiates from sibling tools like sec_ftd_history, sec_ftd_compare, and sec_ftd_search_securities through 'latest' and 'one exact ticker' language.

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 concrete use-case phrasing: 'Use this for "latest reported FTD balance for GME" or "what was the most recent AMC fail balance by June 30?".' It clearly signals when to call this tool, though it does not explicitly state when to prefer sec_ftd_history or sec_ftd_compare instead.

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