list_pix_keys

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

Annotations already declare readOnlyHint=true, and the description consistently says 'Lists,' so there is no contradiction. The description adds the environment limitation ('Only available in environment='mock'') and the Open Finance context, which go beyond the annotation. It does not disclose error scenarios or consent requirements, but the output schema reduces the need for return-format details.

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?

The description is well-structured with a one-sentence purpose, a usage notice, and clearly labeled Args/Returns sections. It is front-loaded and free of fluff. Minor deductions for the 'see module docstring' note and the extraneous ctx parameter, but overall it is appropriately compact.

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?

Given the tool's moderate complexity, an output schema, and readOnlyHint annotation, the description covers the essential elements: what the tool does, the mock-only restriction, and all parameters. It could strengthen completeness by mentioning that consent must exist for the bank account, especially since sibling consent tools are present, but the description is sufficient for selecting and invoking the tool in the intended environment.

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?

With schema description coverage at 0%, the description must compensate. It does explain subject_id as 'User's CPF' and bank as 'Identifier of the participating bank,' but account_id is merely restated as 'Account ID,' adding little meaning. The inclusion of ctx as an argument is confusing because it is not in the input schema, diluting the clarity of the actual exposed parameters.

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?

The description opens with a specific verb and resource: 'Lists the PIX keys (CPF, email, phone, EVP) registered to a bank account via Open Finance Brasil.' This clearly distinguishes it from sibling tools like initiate_pix or list_accounts by naming both the data type and the exact scope.

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 description states 'Only available in environment='mock'' which is a clear usage constraint. It implies this tool is for mock testing rather than production, and the context signals show no competing PIX-key-listing sibling, so the primary use case is evident. It does not explicitly name alternatives, but the unique resource makes them unnecessary.

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