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

With no annotations, the description carries the safety/behavior burden. It reveals that this is a GET (read-only) endpoint and that company scoping is explicit, which is useful, but it omits whether query is optional, pagination, error behavior, and output characteristics—although the existing output schema reduces the need to explain return values.

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 short, front-loaded, and mostly free of waste. The endpoint path is somewhat technical overhead, but the remaining clauses communicate prerequisites and parameters efficiently.

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 two-parameter report tool with an output schema, the description covers the main invocation facts: explicit company, flat query fields, and required period/year filters. It still leaves a significant ambiguity: the schema marks query as optional/default null while the description says period and year are required query fields, and it does not explain what the report contains beyond the output schema.

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 0%, so the description must compensate. It does so by clarifying that company_name must identify the company explicitly, that query fields are flat, that period and year are the required query fields, and that further filters are discoverable via describe_nextesy_operation. It does not fully reconcile the schema's optional query property with the stated required query fields, but it adds substantial meaning beyond the bare schema.

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 states a specific verb and resource: 'GET /api/v1/reports/vat', making it clear this retrieves a VAT report. It does not explicitly differentiate from nearby siblings like get_vat_profile, get_vat_settings, or list_vats, so an agent must infer that this is the report endpoint rather than a settings/profile tool.

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?

It gives useful prerequisites ('Explicit company required') and required query fields ('period, year'), and points to describe_nextesy_operation for filters. However, it does not say when to choose this tool over get_vat_profile, get_vat_settings, or list_vats, nor does it state whether the query object itself is optional.

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