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

Goes well beyond the annotations (readOnly=false, destructive=true, idempotent=true) by disclosing overwrite semantics with no retained old value, warning that this matters for bank details printed on invoices, and clarifying that only new invoices pick up the change while existing invoices retain their original sender details. The onboarding prerequisite is also stated, which no structured field carries.

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 action and field inventory, then the overwrite warning, then the invoice-impact consequence and the onboarding caveat. It is dense with long parenthetical enumerations, but each clause (especially the bank-details warning and the new-vs-existing invoice rule) earns its place.

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 29-parameter, zero-required mutation with no output schema, the description covers side effects, scope of effect on existing invoices, and the blocking precondition. It does not say what the call returns on success or how validation failures surface, which is the only material gap.

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 baseline would be 3, but the description adds value by grouping the 29 parameters into meaningful families (address, tax/VAT, bank, invoice defaults, DATEV) and by stating that only supplied fields are changed, which clarifies that every field is optional. It still gives no per-parameter format or unit guidance beyond what the schema documents.

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 ('Changes the account's sender settings') and enumerates the field families covered: company/address, tax and VAT IDs, bank details, invoice defaults, DATEV numbers. It explicitly contrasts with the sibling read tool, so an agent can separate it from get_sender_settings without opening a schema.

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?

Names the alternative explicitly ('get_sender_settings returns the current values') and gives a hard precondition: it cannot create settings for an account that has not finished onboarding in the web app. The when-to-use is stated ('use it to change any of these'), and the read counterpart is routed away.

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