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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description usefully names the fields returned and the underlying endpoint, but adds nothing about auth, error behavior for a missing package_id, or any rate limits.

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?

Single front-loaded sentence covering resource, key, return fields, and endpoint, with no redundant text. Every clause carries 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?

With no output schema, the description compensates by enumerating the return contents (status, cycle, pay method, next invoice date, line items). For a simple single-resource read this is nearly sufficient; only error/not-found behavior is unaddressed.

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 single 'id' parameter is fully documented as the package_id. The description repeats that mapping ('by package_id') without adding format, bounds, or lookup guidance beyond the schema.

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 one subscription (package) by package_id') and enumerates the salient returned fields, so an agent can distinguish it from chargeover_list_subscriptions at a glance. The endpoint 'GET /package/{package_id}' reinforces the single-resource scope.

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 phrase 'Get one subscription ... by package_id' implies usage, but the description never states when to use this versus chargeover_list_subscriptions or other get_* siblings, nor any prerequisites. Usage is inferable but not prescribed.

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