lemon-squeezy-mcp

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions listing and optional filtering, but lacks critical details: it doesn't specify if results are paginated (though 'page' parameter implies it), what the default ordering is, whether it requires authentication, rate limits, or what the output format looks like. For a listing tool with zero annotation coverage, this is a significant gap.

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 single, efficient sentence that front-loads the core purpose ('List subscription invoices') and adds a brief qualifier ('optionally filtered by subscription'). There is zero waste or redundancy, making it appropriately concise for a simple listing tool.

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 lack of annotations and output schema, the description is incomplete. It covers the basic purpose but misses behavioral context (e.g., pagination behavior, authentication needs) and output details. For a tool with two parameters and no structured safety or output information, more guidance is needed to ensure reliable agent use.

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 schema already fully documents both parameters ('subscriptionId' and 'page'). The description adds marginal value by mentioning optional filtering by subscription, which aligns with the 'subscriptionId' parameter, but doesn't provide additional semantics beyond what's in the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 states the tool's purpose: 'List subscription invoices' with optional filtering by subscription. It specifies the verb ('List') and resource ('subscription invoices'), making the function unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'get_subscription_invoice' (singular) or 'generate_subscription_invoice', which would be needed for a perfect score.

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 minimal guidance: it mentions optional filtering by subscription, but offers no explicit advice on when to use this tool versus alternatives. For example, it doesn't clarify when to choose 'list_subscription_invoices' over 'get_subscription_invoice' (singular) or how it relates to other listing tools like 'list_orders'. No exclusions or prerequisites are stated.

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