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

Annotations already declare the read-only, open-world, non-destructive profile, yet the description still adds substantial behavior the annotations cannot convey: timestamps lacking an explicit timezone, preservation of source values and quality codes, SI normalisation of hydrological units, provenance returns, anonymous rate limits (60/hour, 300/day) with key-based fallback, and source licence warnings. That is genuinely useful context for an agent.

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?

Purpose and scope are front-loaded in the first sentence, followed by return-value, unit and rate-limit facts. The prose is dense and packs several operational facts into a single block, but every clause carries actionable information, so it is efficient rather than bloated.

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 must cover return values, and it does (source data, provenance, timestamps without timezone, quality codes, SI units). Combined with annotations covering the safety profile and the description covering rate limits and licensing, an agent has everything needed to call 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 four parameters are already documented, and the baseline is 3. The description reinforces the start/end 7-day ordering constraint and the timezone caveat on returned timestamps, but adds little syntax or format meaning beyond the schema itself.

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 first sentence states a specific verb (Get), resource (NRW telemetry readings), identifier (measure_id) and scope ceiling (at most 7 days), which is far beyond a tautology. It does not, however, explicitly differentiate itself from readings-style siblings such as flood_get_readings, tide_readings or sepa_values, so it stops short of a 5.

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: requiring a measure_id suggests chaining from nrw_measures, and the 7-day cap constrains the request window, but no sentence tells the agent when to pick this tool over alternatives or when-not to use it. Adequate but with a clear gap.

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