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 successfully describes authentication requirements ('Requires company API token'), gateway-specific behavior ('Required for PayFabric; optional for others'), and integration workflow. However, it doesn't mention rate limits, error conditions, or response format details, which would be helpful for a credential-fetching tool.

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 front-loaded purpose and subsequent usage details. Every sentence adds value, though some sentences are moderately complex. Minor improvements could be made to sentence flow, but overall it's appropriately sized for the tool's complexity.

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 2-parameter tool with no annotations and no output schema, the description provides good coverage of purpose, usage, and behavioral context. It explains the integration workflow and gateway-specific requirements well. However, without an output schema, it could better describe the returned credential format and any limitations or error responses.

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?

With 100% schema description coverage, the baseline is 3. The description adds meaningful context beyond the schema by explaining when customerId is needed ('Optional customerId scopes the credential to a customer') and providing gateway-specific requirements ('Required for PayFabric gateway'). However, it doesn't elaborate on gatewayId semantics beyond what's in 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?

The description clearly states the specific action ('Get the gateway client credential') and resource ('to initialize your payment integration'), distinguishing it from sibling tools like 'create_customer_payment_method' which uses the output. It explains the credential's purpose for producing a paymentMethodNonce and integration with hosted payment UI, providing a complete functional overview.

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 explicitly states when to use this tool ('Required for PayFabric; optional for others') and provides clear alternatives and next steps ('Use the returned value in your hosted payment UI; then pass the resulting token as paymentMethodNonce to create_customer_payment_method'). It also specifies prerequisites ('Requires company API token') and contextual constraints ('Gateway-agnostic: no gateway-specific concepts in MCP').

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