bank_accounts_update

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

Annotations already declare non-read-only, idempotent, non-destructive, so the safety bar is lower. The description still adds genuine behavioral value: the one-way lock on openingBalance once persisted >0 and the redirect of corrections to cash movements — a non-obvious irreversible-effect warning not captured by annotations.

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?

Three tight sentences: purpose first, then the lock constraint, then the minimum-input rule. Every sentence carries decision-relevant information with no padding.

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 9-parameter mutation tool with full schema coverage and no output schema, the description covers preconditions and the irreversible lock. It could note the return shape or confirm idempotent re-application semantics, but nothing critical to correct invocation 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 description coverage is 100%, so the schema already documents every parameter including the null-clearing semantics and the openingBalanceDate requirement. The description's field list largely restates the schema and adds little format/validation detail beyond it, so baseline 3 applies.

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 ('Update an existing bank account') and enumerates the mutable fields (type, IBAN, bank name, currency, default status, opening balance), which lets an agent distinguish it from bank_accounts_create or cash_register_movements_update. It stops short of naming those siblings explicitly, so no explicit differentiation is given.

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?

'At least one field must be provided' gives a clear invocation precondition, and the statement that corrections must go through cash movements after openingBalance is locked effectively routes the agent to an alternative tool. It does not explicitly cover when to prefer create vs update or company-scoping choice, but the operational context is clear.

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