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

Annotations already declare readOnly/idempotent/non-destructive/open-world, so the safety profile is covered. The description adds meaningful non-schema context: a SibFly key is required for the full series ($0.40) while keyless access returns a coverage teaser, plus a distinction between measured (premium frames) and modeled (fitted) data.

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?

Front-loads the core purpose, then usage intent, then the measured/modeled semantics and the auth/pricing caveat. Dense but every sentence carries information; no filler or tautology.

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?

For a read-only time-series tool with no output schema, the definition covers what is returned, how to invoke it (address or lat/lon), the series_type nuance, and the key/pricing model. Only minor gaps remain, such as output shape or point spacing, which are not essential to selection.

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 the baseline is 3 and the schema already documents all five parameters. The description adds marginal meaning beyond it by clarifying that 'measured' uses premium frames and 'modeled' fits a trend on real acquisition dates, and that only a keyed call yields the full series.

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 resource (historical ground-motion time series) and its nature (per-date satellite measurements of vertical displacement over time, month by month). It also implicitly distinguishes itself from the current-velocity sibling (sibfly_ground_motion) by framing itself as the TREND tool 'not just the current velocity.'

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?

Explicitly says when to use it ('to see the TREND of subsidence/uplift, not just the current velocity'), which routes the agent away from a velocity-oriented sibling. However, it never names the alternative tool (e.g. sibfly_ground_motion) or states a hard exclusion, so routing is inferred rather than explicit.

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