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

Going well beyond the annotations, the description discloses anonymous rate limits (60/hour, 300/day per IP and session), that no API key is needed, quota fallback behaviour, SI normalisation of hydrological units, provenance/licence warnings, and that source data is returned. These are exactly the operational facts an agent needs and none of them are in the structured fields.

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 core purpose and return contents are front-loaded in the first two sentences, with rate-limit and licensing details following usefully. One sentence, "TerraMCP is a Wrench AI service", is pure branding filler that does nothing for tool selection.

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 burden for return values and does so adequately (series IDs, units, source data, provenance). Auth and rate-limit context is thorough; only pagination/limit interaction is left entirely to the schema.

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 baseline is 3. The description restates "station_id (station number)", which matches the schema's SEPA station_no semantics, but adds no new meaning and says nothing about the limit parameter beyond what the schema already documents.

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 states a specific verb and resource: "List bounded SEPA KiWIS time series for a station_id", and clarifies what is returned (series IDs, reported units/OGL). It is clearly distinguishable from sepa_values (readings) and sepa_stations (station discovery) by the word "series", though it never names those siblings explicitly.

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 tool is the middle step of the stations -> series -> values pipeline, and the description hints at discovery by promising series IDs and units. However, it never says when to prefer sepa_series over sepa_values, nor that station_id must first come from sepa_stations (that constraint lives only in the schema).

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