YNAB MCP Server

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

With no annotations provided, the description carries the full burden. It discloses that it's a read operation ('List') and mentions balance details, but does not cover behavioral aspects like error handling, pagination, rate limits, or authentication needs. The description is adequate but lacks depth for a tool with no annotation support.

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 front-loaded with a clear purpose statement, followed by structured 'Args' and 'Returns' sections. Every sentence adds value without redundancy, making it efficient and well-organized for quick understanding.

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 low complexity (1 parameter) and the presence of an output schema (which handles return values), the description is mostly complete. It covers the purpose, parameter semantics, and return structure, but could improve by addressing behavioral transparency gaps like error cases or usage constraints.

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 0%, so the description must compensate. It explains that 'budget_id' is optional and uses a default if omitted, adding meaningful context beyond the schema. However, it does not detail what the default is or provide examples, leaving some gaps.

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 clearly states the verb ('List') and resource ('all accounts in a budget with balances'), making the purpose specific and actionable. It distinguishes itself from siblings like 'get_budgets' or 'get_transactions' by focusing exclusively on accounts with balance information.

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 implies usage by specifying 'in a budget' and noting that 'budget_id' uses a default if omitted, providing some context. However, it lacks explicit guidance on when to use this tool versus alternatives like 'get_budgets' or 'create_account', and does not mention prerequisites or exclusions.

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