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

With no annotations, the description carries the full burden and does: it discloses that nothing is deleted, the original is retained and linked, the reversal entry is returned, and VAT postings/open items/document side effects are unwound. It also lists the specific 409 triggers and the closed-period correction procedure, which is exactly the behavioral context an agent needs before invoking a mutation.

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-loaded with the outcome in the first line, then parameter behavior, then failure modes — a logical progression. Markdown bolding and backticks add slight visual noise, but every sentence carries 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?

No output schema exists, yet the description states the reversal entry is returned; it covers side effects, defaulting behavior, closed-period handling, and the full set of 409 reasons. Nothing an agent needs to call this mutation safely is missing.

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 coverage is 0%, so the description must compensate. It does for the one non-obvious parameter: body.posting_date determines the reversal's date and period, and defaults to the original's date when omitted. entry_id and company_id are left implicit, which is reasonable since their meaning is self-evident, but it keeps this from a 5.

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 ('Storno a posted journal entry: post its mirror image') and scopes it to an accountant role. The word 'Storno' plus 'mirror image' makes clear it is not the same as create_gl_journal_entry or post_gl_journal_entry, even without reading their schemas.

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 only VAT-correct storno door' explicitly routes the agent here rather than to a manual reversal, and the 409 paragraph enumerates concrete conditions where the call will fail. It stops short of naming alternative siblings or a fallback path when a 409 occurs, so not quite a 5.

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