Rebillia MCP Server

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions the HTTP method (POST) and required/optional parameters, but fails to describe important behavioral aspects: whether this is a mutating operation, what permissions are needed, how it affects billing, what happens on success/failure, or any rate limits. For a tool that modifies subscription data, this leaves significant gaps in understanding its impact.

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 reasonably concise but poorly structured - it mixes API endpoint details with parameter information in a single run-on sentence. While it front-loads the core purpose, the parameter details could be better organized. Some information (like the HTTP method) may be unnecessary if the agent understands REST conventions.

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 mutating tool with 7 parameters and no annotations or output schema, the description is insufficient. It doesn't explain what the tool returns, how errors are handled, what side effects occur, or how this operation fits into broader subscription management workflows. The lack of behavioral context makes it difficult for an agent to use this tool confidently.

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 documents all 7 parameters thoroughly. The description adds minimal value beyond the schema - it mentions 'required: productRatePlanId' and lists optional parameters, but provides no additional context about parameter interactions, business logic, or usage examples that aren't already in the schema descriptions.

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 action ('Add a rate plan to a subscription') and identifies the resource ('subscription'), making the purpose immediately understandable. However, it doesn't explicitly differentiate this tool from its sibling 'add_subscription_rate_plan_charge' or other subscription-related tools, which would require more specific context about when to use each.

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 no guidance on when to use this tool versus alternatives like 'create_subscription' or 'update_subscription_rate_plan'. While it mentions the required 'productRatePlanId', it doesn't explain prerequisites, dependencies, or appropriate contexts for adding rate plans versus other subscription operations.

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