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

Annotations already declare destructiveHint=true and openWorldHint=true, so the mutation risk is covered structurally. The description adds genuine context beyond that: a hard cap of 12 accounts and the fact that changing an entry is keyed by an existing id rather than creating a new one. It stops short of saying what happens to branches already pointing at an account that is modified.

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?

Two sentences, front-loaded with the gating precondition before the mechanics. Dense with cross-references and backticked paths, but every clause carries information; the trailing 'Up to 12' is terse but earns its place as a hard limit.

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?

With four parameters at full schema coverage, annotations covering safety, and no output schema to explain, the description supplies everything else an agent needs: the precondition, the id source, the downstream wiring step, and the count ceiling.

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 baseline is 3, but the description adds provenance the schema lacks: the id originates from get_overview `brands[].profile.payeeGroups`, and the account is consumed downstream via save_branch payeeGroup. That linkage is real value beyond the per-field descriptions.

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 ('Add an account, or change one by its id') and immediately scopes it against the sibling that handles the primary account ('account 1, set with update_settings paymentDetails'). An agent can distinguish this from update_settings and remove_payment_account without opening any 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?

Opens with an explicit precondition ('Only if some branches are paid into a different account than the main payment details'), names the tool that handles the excluded case (update_settings paymentDetails), and gives the follow-up step (save_branch payeeGroup). When-to-use, when-not-to-use, and alternatives are all present.

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