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

Annotations already mark it read-only and idempotent, but the description adds behavioral specificity: it returns the canonical public catalog including monthly USD prices and allowances, and explicitly disclaims selection/checkout/billing effects.

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?

Two short sentences with the core action front-loaded. No filler, no repetition of the tool name, and every clause adds information.

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 zero-parameter, read-only list tool with an output schema available, this description is complete: it states what the agent will retrieve, the format/scope (monthly USD prices and allowances), and what will not happen.

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?

The tool has zero parameters, so there is no parameter ambiguity. The description adds useful context about the returned data (monthly USD prices and allowances), which is the baseline expectation for a parameterless catalog lookup.

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?

Opens with a specific verb and object: 'Read the canonical public KaiCalls plan catalog.' It also clarifies what the tool does not do (select a plan, create checkout, or change billing), distinguishing it clearly from action-oriented siblings.

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?

Provides clear read-only context and explicitly excludes side-effect actions like checkout creation and billing changes. It stops short of routing the agent to a specific sibling tool for those actions, so it is not a full 5.

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