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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), yet the description still adds meaningful substance: the source join, bounded/paginated output, two-decimal share, run id, source hashes, vintage, and methodology caveats. It does not disclose auth/rate-limit behavior, which keeps it short of a 5.

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?

Two sentences with no filler, and the defining scope statement is front-loaded. The leading rhetorical question is slightly indirect framing but is not wasteful.

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 carries the return-value burden and does so well, listing USD-million values, the two-decimal share, run id, source hashes, vintage, and caveats. It leaves minor gaps (no explicit pagination default behavior), but an agent has enough to invoke 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 description coverage is 100%, so all five parameters are already documented. The description only echoes the pagination ('bounded/paginated') and date-window concepts without adding format or constraint detail beyond the schema, so the baseline of 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?

The description names a specific computed metric (foreign official institutions' share of total foreign Treasury holdings), describes its source join (MFH Foreign Official memo line to Grand Total), and explicitly frames it as 'a custodial aggregate, not a country allocation or investment signal,' which cleanly separates it from holder/ranking siblings like treasury_tic_compare_holders and treasury_tic_find_holders.

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?

Usage is only implied. The exclusion clause ('not a country allocation or investment signal') tells the agent when NOT to reach for this tool, but no alternative sibling is named and no positive routing condition (e.g., 'use this to track official-sector share over time') is stated.

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