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

Beyond the annotations (readOnlyHint=true, destructiveHint=false), the description adds meaningful context: it enumerates the returned fields, specifies the ownership restriction, and notes the required billing scope. This gives the agent a richer operational picture than the annotations alone.

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 description is a compact two-sentence structure with no unnecessary words. It front-loads the core purpose and then adds essential access constraints, making it highly efficient and scannable.

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?

Given the tool has no parameters, no output schema, and minimal annotations, the description fully covers the agent's needs: exactly what data is returned and the prerequisites for invocation. There is no ambiguity about the action or its outcomes.

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 the schema provides no parameter semantics. Per the baseline rule for zero-parameter tools, the description need not add parameter details. The description appropriately explains the fixed output, so a baseline of 4 is fitting.

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 clearly identifies the operation ('Get the project owner's current subscription') and lists the exact data returned (plan, active flag, period start/end, cancel-at-period flag, Paddle subscription ID, payment method status). This distinguishes it from sibling tools like get_billing by focusing specifically on subscription details.

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 provides clear access constraints: 'Owner-only' and 'requires a token minted with the billing scope.' This tells the agent who can use it and what credentials are needed. However, it does not explicitly name alternatives or provide when-not-to-use guidance beyond the ownership restriction.

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