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

There are no annotations, so the description carries the behavioral disclosure burden. It reveals the authentication prerequisite, the re-invocation workflow, and the fact that start_login will not satisfy the requirement. It does not describe error behavior or response shape, but the key access behavior is transparent.

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 compact and front-loaded: the core purpose appears first, followed by the essential access instruction. Every sentence earns its place, and there is no redundant or speculative wording.

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-style tool with no output schema, the description is nearly complete: it states what the tool returns, the access requirement, and the authentication workflow. It stops short of explicitly guiding an agent to choose this over get_usage or describing the response format, but the tool's simplicity keeps this gap minor.

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 and schema coverage is 100%, so no parameter documentation is needed. The description adds value by naming the returned fields (plan, status, billing period, usage limits), which helps an agent infer what the output will contain.

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 opens with a specific verb and resource: 'Get the current subscription details' and enumerates concrete fields (plan, status, billing period, usage limits). This clearly distinguishes it from sibling tools like get_usage or get_platform_summary, which focus on different aspects.

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 usage context: a Proof account is required, the client must be authenticated via the MCP authentication flow, and the tool should be called again after authenticating. It also warns that start_login does not open this tool, acting as a when-not signal, though it does not compare against other subscription/usage siblings.

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