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

Annotations already declare readOnlyHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds real substance beyond that: it discloses the exact response payload (metadata block plus windowed summary plus newest points), which tells the agent this is a self-contained single-series fetch rather than a list. It does not mention point-count limits, truncation of 'newest points', or behaviour on unknown ids.

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?

The what-you-get content is front-loaded in the opening sentence and the actionable instructions (window narrowing, id provenance) follow compactly. The ten-publisher enumeration is the one indulgence — useful for coverage signalling but the longest part of the text and not needed to invoke the tool.

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 full burden of explaining return values and does so explicitly. Combined with the id-source pointer and the date-format guidance, an agent has everything needed to construct a correct call and interpret the result for a simple three-parameter read tool.

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%, so from/to formats are already documented and the description largely restates them (YYYY, YYYY-MM, YYYY-MM-DD). The genuine value added is the provenance of the required id — 'Series ids come from list_datasets' — which the schema does not say and which prevents a failed call. That lifts it above the baseline 3.

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 the concrete resource (one mirrored statistical series) and enumerates exactly what comes back: publisher, unit, licence, period range, a window summary (latest value per category, min, max, first-to-last change) and newest points. It also distinguishes itself from list_datasets by stating that series ids come from that tool, so an agent can tell the enumeration tool from the fetch tool.

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 clear operational context: use from/to to narrow the window, and obtain the id via list_datasets first. Format expectations for the date arguments are spelled out. What's missing is any exclusion or alternative routing — for example when gcc_series or oil_balance would be the better pick — so the guidance is clear but not exhaustive.

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