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

Annotations already carry the safety profile (readOnly, non-destructive, openWorld), and the description adds materially more: anonymous rate limits (60/hour, 300/day per IP and session), keyed higher limits with fallback after monthly quota, open-data/no-signup status, licence warnings, SI normalisation, and retention of datum qualifier and original unit.

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, unit/datum behaviour, and the predictions exclusion are front-loaded before the operational boilerplate. Most sentences earn their place (rate limits, licence), though 'TerraMCP is a Wrench AI service' adds little 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?

There is no output schema, so the description must cover returns, and it does: source data plus provenance, SI normalisation, retained datum qualifier and original unit. Combined with quota/auth context, an agent has everything needed to call and interpret this 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 both parameters (station_id, latest_n) are already documented with patterns, bounds, and defaults. The description adds only output-oriented context (SI metres, datum/unit retention) and no extra parameter semantics, so the 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?

States a specific verb and resource ('Get latest observed tidal levels for an EA station') and explicitly scopes it as observations, not predictions ('Not tide predictions'), which separates it from prediction-style siblings and complements the discovery tool tide_stations named in the schema.

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?

Gives clear context ('to inspect coastal water levels') and an explicit exclusion (not tide predictions), and the schema points to the provider's station discovery tool for the required station_id. It doesn't name the discovery sibling (tide_stations) directly in the description, so the routing is strong but not fully explicit.

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