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

Annotations already provide readOnlyHint=true, and the description reinforces this with 'one read' and 'Basis: SST-02 return figures + the consolidated-e-invoice register.' It adds meaningful conditional behavior about unregistered users and the e-invoice consolidation statuses, going beyond what the annotation alone conveys.

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 front-loaded summary sentence and numbered components. Every clause adds useful information, and the parenthetical clarifications are compact rather than redundant.

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?

For a zero-parameter, read-only status tool with no output schema, the description is complete: it names both reporting areas, the source basis, the conditional SST behavior, the open period, due date, and validation status. An agent has enough to know what this tool returns and when the data is meaningful.

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 tool has zero parameters and the schema coverage is effectively 100%, so there is no parameter-meaning burden for the description to carry. The baseline for a no-parameter tool is 4, and the description does not need to add anything further.

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 opens with a clear verb and target ('Your current tax posture in one read') and then enumerates the two specific components covered: SST payable and e-invoice consolidation. This makes the tool's scope unmistakable and distinct from the many summary siblings like cash_position or business_snapshot.

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 clearly implies this is the tool for a consolidated tax-status check, and it clarifies the conditional handling for SST registration ('registration 'none' ⇒ not registered, nothing to remit'). However, it does not explicitly name alternative tools or state when not to use it, so it misses the explicit exclusion guidance that would earn a 5.

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