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 for behavioral disclosure. It states this is an update operation (implying mutation) and shows the return format, but doesn't address important behavioral aspects like: what permissions are required, whether updates are atomic, what happens with partial updates, error conditions, or rate limits. The description adds minimal behavioral context beyond the basic operation.

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 clear purpose statement followed by Args and Returns sections. Each sentence earns its place, though the 'Returns' statement could be slightly more specific. The formatting with sections makes it easy to parse, though it's not perfectly front-loaded (the key purpose comes first, but details follow in sections).

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 this is a mutation tool with no annotations but with an output schema (implied by 'Returns' statement), the description covers the basic operation and parameters well. However, for a tool that modifies financial data, it lacks important context about permissions, validation rules, error handling, and transactional behavior. The presence of an output schema reduces the need to describe return values, but behavioral context remains incomplete.

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 0% schema description coverage, the description must compensate, and it does so effectively. It explains all 5 parameters: category_id (UUID), name (new name), note (new note), goal_target (milliunits with example), and budget_id (default behavior). The goal_target example (500000 = $500.00) is particularly valuable. However, it doesn't explain null handling for optional 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 clearly states the tool updates specific attributes of a category (name, note, goal target) with a specific verb+resource combination. It distinguishes itself from sibling tools like 'update_month_category' by focusing on category-level updates rather than month-specific category updates. However, it doesn't explicitly contrast with 'get_categories' or other update tools beyond the title difference.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention when to prefer 'update_category' over 'update_month_category' or when category updates are appropriate versus other operations. The only contextual hint is the budget_id parameter default behavior, but this isn't framed as usage guidance.

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