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

With no annotations, the description must carry the burden of behavioral disclosure. It only states what the tool checks, but does not mention whether it is read-only, what happens on mismatch, or what the return value/response looks like. This lack of behavioral detail 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, clear sentence that conveys the core purpose without any unnecessary words. It is front-loaded with the verb and resource, making it immediately understandable.

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?

While the tool is simple (one parameter, no output schema), the description omits what the result of the check is (e.g., boolean, error message). Without an output schema, the description should clarify the return behavior, which is critical for an agent to know how to handle the response. This incompleteness leaves a significant gap.

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?

The single parameter 'pdf_content' is well-described in the schema (base64-encoded ZUGFeRD PDF content), providing 100% coverage. The description itself adds no additional parameter meaning, but the schema is sufficient, so baseline 3 is appropriate.

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 a specific action ('Prüft' - checks) and a specific resource/scope (whether visible PDF data matches embedded XML data). It also distinguishes itself from siblings like create_invoice and validate_invoice by focusing on consistency between two data representations.

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 implies its usage for verifying consistency but offers no explicit guidance on when to use it versus alternatives like validate_invoice or extract_xml. It does not mention prerequisites or exclusions, so the usage context is inferred rather than stated.

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