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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: it discloses paginated bounded USD-million output, a two-decimal share per month, and returned metadata (run id, exact official source hashes, vintage, methodology caveats). That is real behavioral and lineage context for a query tool.

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 dense sentences, front-loaded with the core question before mechanics and caveats. Every sentence earns its place, though domain jargon ('MFH Foreign Official memo line', 'vintage') assumes familiarity.

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 correctly carries the return-value burden by listing returned fields (values, share, run id, hashes, vintage, caveats), and annotations cover the safety profile. Nothing an agent needs to call it correctly 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 all five parameters (limit, offset, start/end month, response_format) are already documented. The description adds only framing ('bounded/paginated', 'fixed monthly window', 'USD-million') without new syntax or constraint detail beyond the schema, so 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?

Opens with a precise verb+resource+metric ('what share of total foreign Treasury holdings... for foreign official institutions over a fixed monthly window') and names the exact join (MFH Foreign Official memo line to Grand Total). It also explicitly distinguishes itself from sibling holder/rank tools by stating 'This is a custodial aggregate, not a country allocation or investment signal.'

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?

It gives a negative scope statement ('not a country allocation or investment signal') that implicitly steers away from holder-level siblings, but it never names an alternative tool or states the concrete condition that selects this one over treasury_tic_find_holders / treasury_tic_compare_holders. Usage is implied rather than directed.

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