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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds meaningful value: 'Sends nothing to SDI and changes nothing' explicitly scopes the side effects, it discloses the return content (validation errors, with a date-field example), and it states the Cotlet API key access requirement. Only the exact error payload shape is left unspecified.

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?

Front-loads the purpose, then layers the no-side-effect guarantee and the remediation workflow. Slightly long at five sentences, and 'sends nothing to SDI' partially overlaps the readOnlyHint annotation, but each sentence carries usable information.

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?

With no output schema, the description usefully covers the return contract (validation errors) and the auth prerequisite, which is enough for an agent to call and interpret this two-parameter read tool. Minor gap in not describing whether results are structured or free-text, but adequate overall.

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% for both parameters, so company_id and invoice_id semantics are already fully documented. The description adds no syntax or format detail beyond implying the invoice identity, so baseline 3 is correct.

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?

States a specific verb and resource ('Check an invoice's e-invoice XML for errors') and frames its role against the SDI submission flow, distinguishing it from siblings like send_einvoice and get_einvoice_status. An agent can tell immediately that this is a dry-run validator.

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?

Clearly says to use it 'before sending it to SDI' and describes the fix-then-reverify loop, which implies the pre-submission workflow. It stops short of naming sibling alternatives (e.g. get_einvoice_status) that an agent might otherwise pick, so it is clear context without explicit exclusion.

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