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

Annotations indicate readOnlyHint=false (mutation) and no destructive flag. The description supplements with context about on-chain visibility of session and vault PDAs and security warnings. It does not contradict annotations.

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 well-structured with a clear first sentence stating purpose, followed by contextual and usage information. While it contains some repetition (e.g., pricing/routing duplicated in schema description), it remains focused and mostly concise.

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 complexity of the SAP MCP ecosystem and the presence of an output schema, the description covers purpose, usage boundaries, and security implications. It lacks explicit mention of return value details but is sufficient for the agent to use the tool correctly.

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 tool description does not add extra meaning to the single parameter beyond what the schema already provides. The schema description adequately explains accepted formats (byte array, hex, base64).

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 ('Open a vault session') and the required input (32-byte session hash). It is specific and distinguishable from sibling tools, though it does not explicitly differentiate from similar session-related tools (e.g., sap_session_start).

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 extensive guidance on when to use this tool, including pricing model, routing restrictions, and alternatives like sap_payments_call_paid_tool. It explicitly states when not to call it and what to use instead.

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