YNAB MCP Server

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

With no annotations provided, the description carries full burden. It indicates this is a read operation ('List') and specifies temporal scope ('current month'), but doesn't mention permissions needed, rate limits, pagination, or error conditions. It provides basic behavioral context but lacks operational 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 clear sections (purpose, args, returns) and uses minimal sentences. The first sentence efficiently conveys the core functionality, though the 'Args' and 'Returns' labels could be integrated more seamlessly.

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 (read operation with one optional parameter) and the presence of an output schema (which handles return value documentation), the description is reasonably complete. It covers purpose, parameter semantics, and return content at a high level, though could benefit from more behavioral context.

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?

The description adds meaningful context for the single parameter: it explains that budget_id is optional ('uses default if omitted') and clarifies its purpose ('Budget ID'). With 0% schema description coverage and only one parameter, this adequately compensates for the schema gap.

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 action ('List all category groups and categories') and specifies the exact data returned ('budgeted/activity/balance for the current month'). It distinguishes from siblings like get_accounts or get_transactions by focusing specifically on categories with financial metrics.

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 for retrieving category data with monthly financial info, but doesn't explicitly state when to use this vs alternatives like get_month (which might provide similar data) or update_category (for modifications). No explicit exclusions or prerequisites are mentioned.

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