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

With no annotations, description fully discloses input formats and the three validation steps. No contradictions. Could mention output format, but output schema exists. Good transparency for a read-only validation 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?

Four concise, front-loaded sentences. Each sentence adds unique value: purpose, input format, validation details, and authentication status. No wasted words.

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 tool's complexity (2 params, 0% schema coverage, no annotations), the description covers input, validation behavior, and authentication. Output schema exists so return values are not needed. Could mention error handling, but overall complete.

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 has 0% description coverage; description compensates by explaining the 'content' parameter accepts base64-encoded PDF or raw CII XML and mentions default format. Adds significant meaning beyond the schema's bare titles.

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?

Description clearly states the tool validates existing ZUGFeRD/Factur-X/E-Rechnung invoices, listing specific formats (PDF, CII XML) and validation checks (PDF/A, EN 16931, KoSIT). This distinguishes it from sibling tools like compliance_status and generate_einvoice.

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?

Explicitly states 'No authentication required' and implies usage for validating existing invoices. Does not explicitly contrast with siblings, but the verb 'validate' clearly differentiates from generation or status checks.

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