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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered without description help. The description adds genuinely useful context beyond that: the data source (synced invoices) and the currency unit (øre), which prevents unit errors. It stops short of disclosing return shape, whether empty quarters appear, or staleness of the synced data.

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?

A single front-loaded sentence with no filler; every element (metrics, granularity, unit, source) carries information. It could be marginally stronger by leading with the verb's object or adding one clause on when to prefer it over profit_and_loss.

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?

The tool is simple (2 params, read-only), but there is no output schema, so the description bears responsibility for conveying the return shape. It names the three metrics and unit but not whether the result is a quarter-keyed map or array, whether all four quarters are always present, or how missing data is represented.

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%, so both parameters (year, connection_id) are already documented, including the 'Default: this year' behavior and the pointer to list_connections. The description adds only the implicit framing that the year scopes a per-quarter breakdown, which the schema does not spell out. Baseline 3 is warranted.

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 combination: it outputs three named VAT figures (output VAT, input VAT, VAT payable) at a stated granularity (per quarter) in a stated unit (øre) from a stated source (synced invoices). The purpose is unambiguous, but it does not differentiate itself from the sibling profit_and_loss report, which likely overlaps in financial-reporting intent.

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?

Usage is only implied: an agent can infer this is the tool for period VAT reporting and that 'synced invoices' means data must already be synced via a connection. There is no explicit when-to-use, no exclusion of profit_and_loss for overlapping queries, and no statement of what happens if the connection has no synced data.

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