Rebillia MCP Server

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

With no annotations provided, the description carries full burden for behavioral disclosure. It partially succeeds by revealing the HTTP method (PUT) and a key implementation detail about price conversion (dollars/cents handling). However, it lacks critical information about side effects (e.g., whether this affects billing immediately, requires specific permissions, or has rate limits), error conditions, or what happens to existing charge data not mentioned in the update.

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 efficiently structured with the core purpose stated first, followed by implementation details and parameter requirements. However, it could be more front-loaded by separating usage guidance from parameter documentation. The sentence about price conversion logic is valuable but slightly disrupts the flow. Overall, it's concise with minimal wasted text.

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 complex mutation tool with 15 parameters, no annotations, and no output schema, the description is moderately complete. It covers the core operation and key parameter details but lacks important context: no information about return values, error handling, side effects, or prerequisites. The absence of behavioral annotations means the description should compensate more thoroughly for what happens during and after the update.

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 baseline is 3. The description adds significant value by clarifying parameter semantics beyond the schema: it explicitly lists required parameters, explains the price field's dual format (dollars/cents) and internal conversion logic, and specifies conditional requirements (billingPeriodAlignment when chargeType is recurring). This goes well beyond what the schema provides, though it doesn't cover all 15 parameters individually.

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 specific action ('Update a rate plan charge on a subscription') and identifies the exact resource being modified. It distinguishes itself from sibling tools like 'add_subscription_rate_plan_charge' (which creates new charges) and 'update_subscription_rate_plan' (which updates different subscription components), making the purpose unambiguous.

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. It doesn't mention prerequisites (e.g., needing an existing subscription and charge), compare with similar tools like 'update_subscription' or 'update_product_rate_plan_charge', or specify scenarios where this update is appropriate versus creating new charges. Usage context is entirely implied from the tool name alone.

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