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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely non-obvious context beyond that: the output carries provenance signals (disclosed %, high-confidence %, ECB reconciliation Δ), which tells the agent the numbers are estimates with confidence metadata rather than exact figures. It does not mention cost/latency or empty-period behaviour.

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?

One dense sentence plus a positioning clause, with the core action front-loaded before the metric list. The enumeration is long but each item maps to a real output category, so little is wasted; the em-dash stack is slightly hard to scan but nothing is padding.

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?

There is no output schema, so the description must explain the return payload itself — and it does, listing totals, splits, concentration, dimensional breakdowns and provenance metrics. For a one-optional-parameter, read-only aggregate tool this is sufficient to call correctly and interpret the result.

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% and the single 'period' parameter already documents all accepted formats (year, half, quarter, month) plus the current-year default. The description only repeats 'for a period' and 'Defaults to the current year', adding no new syntax or semantics. 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?

A concrete verb ('aggregate') plus a scoped resource ('European funding picture for a period'), followed by an explicit enumeration of what the aggregate contains (totals split by instrument, concentration, country/sector/stage breakdowns, provenance). It is immediately distinguishable from sibling tools like search_rounds and search_exits, which return individual records rather than aggregates.

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 phrase 'Beats paging every round to sum client-side' explicitly frames the tool as the alternative to iterating search_rounds, giving a clear use context. The default period behaviour is stated. It stops short of naming when NOT to use it (e.g. when you need per-round detail, call search_rounds), so it falls just short of a 5.

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