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

Adds a genuinely valuable behavioral disclosure beyond the destructiveHint annotation: 'creates a record only — it MOVES NO MONEY,' which directly addresses an agent's main risk concern for a banking tool. It does not, however, mention idempotency, permissions, or what side effects follow from later referencing this record.

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 tight sentences, front-loaded with the purpose and the safety clarification, plus the API endpoint. Every clause carries information; nothing is 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 flat five-parameter creation tool with no output schema, the description covers purpose and the key mutation caveat well. It is slightly incomplete in not indicating what the call returns (the external account ID) or the entity linkage needed for later transfers.

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 all five parameters are already documented in the schema, and the description adds no parameter-level detail (no mention of routing/account number formats or enum values). This matches the baseline for fully documented schemas.

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 ('Registers an external (counterparty) bank account in Increase') and even names the underlying API endpoint POST /external_accounts. An agent can immediately distinguish this from siblings like increase_list_external_accounts.

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?

The phrase 'for future transfers' implies the context of use, but the description never states when to use this versus increase_list_external_accounts or increase_get_account, nor any prerequisites. Usage is inferable but not explicit.

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