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

Annotations already cover read-only, idempotent, closed-world behavior, so the bar is lower. The description adds genuinely non-obvious semantics: rounds/per_currency/undisclosed count equity only while by_category spans all categories, warning that the category split can exceed the round count. That prevents a real misinterpretation, though it says nothing about no-filter defaults or currency conversion of totals.

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 dense sentences: the first lists what is returned, the second front-loads the counting caveat before the reader hits the numbers. No filler and no restatement of the title.

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 does the necessary work of naming the returned aggregates and flagging the category-vs-round discrepancy. It falls slightly short on default behavior when all optional filters are omitted and on how per-currency totals are aggregated.

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% with well-documented from/to/topic/country fields, so the schema carries parameter meaning. The description adds only the implicit notion of a 'slice' being defined by these filters and does not clarify how multiple filters combine or what an empty filter set returns.

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 (counts) and resource (a slice of the funding database) and enumerates the exact aggregates returned: rounds, countries, per-currency totals, undisclosed rounds, and rounds per category. This clearly distinguishes it from listing tools like list_funding_rounds or largest_rounds, which return records rather than counts.

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 routes one case away from this tool by naming list_fund_closes as the separate path for fund closes. It does not, however, explicitly contrast with list_funding_rounds, largest_rounds, or get_funding_index, so the agent must infer that this tool is the aggregate-count option.

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