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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description still adds meaningful non-schema context: the READ:FINANCE scope requirement and the concrete endpoint. It also explains what the returned fields mean (totalBalance in the smallest currency unit, currencyId), which the agent could not infer from the schema alone.

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 resource and the return shape, then the enum semantics, then auth and endpoint — no sentence is filler. The telegraphic fragment style ('Needs READ:FINANCE. GET /v2/...') is terse but every element 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?

There is no output schema, so the description must carry the return shape, and it does name totalBalance and currencyId along with units. Auth scope and endpoint are covered; the only remaining gap is guidance on when to pick this over the neighbouring account/payout tools.

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 100%, so the schema already documents both parameters including the enum. The description restates the LIQUID/PRELIMINARY meanings and the point-in-time option but adds little beyond the schema for the parameters themselves; the 'smallest currency unit' note concerns the response, not inputs.

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+resource ('the merchant's Zettle account balance') and defines the two account variants (LIQUID = available for payout, PRELIMINARY = not yet settled) plus the underlying endpoint. It is clear what the tool returns, but it never names a sibling to contrast with (e.g. zettle_get_account or zettle_get_payout_info), so differentiation is left implicit.

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?

'Optional point in time' implies the historical-balance use case, but there is no explicit when-to-use or when-to-prefer-another-tool guidance, and the boundary with zettle_get_payout_info / zettle_list_account_transactions is unstated. Usage is inferable rather than stated.

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