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

Annotations already provide readOnlyHint=true, and the description adds valuable behavior beyond that: this is a paid call and cost scales with coins × timeframes. It also clarifies the semantic difference between settled last-closed-bar readings and still-forming updates. No contradiction with annotations.

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?

Three tight sentences with no filler. The main operation is front-loaded, the 'kind' distinction is explained immediately, and the cost warning is placed last as supporting context. Every sentence earns its place.

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 paid bulk-read tool with no output schema, the description covers the main things an agent needs: required parameters, the choice between settled and forming readings, and cost behavior. It does not describe the response shape or valid currency identifiers, but given the read-only annotation and simple parameter structure, the description is largely sufficient.

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 only 33%, so the description must compensate. It does explain 'kind' and generally maps 'currencies' and 'tfs' to coins and timeframes, but it does not specify the expected currency string format or any limits on array sizes. It adds some value but leaves part of the parameter semantics to inference.

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 ('Get'), a clear resource ('phases'), and the distinguishing scope ('several coins and timeframes'), which separates it from the singular sibling trendvane_get_phase. It also names the two 'kind' variants, making the operation unambiguous.

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?

The description conveys clear when-to-use context: use this for multiple coins and timeframes in a single paid call, and choose 'boundary' vs 'updates' depending on whether the bar is closed. It does not explicitly list when-not-to-use or point to a single-coin alternative, but the bulk-vs-single distinction is strongly implied.

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