YNAB MCP Server

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

No annotations are provided, so the description carries full burden. It states this creates a new account but doesn't disclose behavioral traits like required permissions, whether this is idempotent, error conditions, or side effects. The Returns section describes output but not behavioral context. For a mutation tool with zero annotation coverage, this is insufficient.

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?

Well-structured with clear sections (Args, Returns), front-loaded purpose statement, and zero wasted sentences. Every element serves a purpose: the first sentence states the tool's function, followed by parameter documentation and return value description.

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 output schema (implied by Returns section), the description covers parameters thoroughly and states what's returned. However, it lacks behavioral context (permissions, errors, side effects) that would be important for a creation tool. The output schema reduces but doesn't eliminate the need for behavioral transparency.

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 fully. It provides clear semantic meaning for all 4 parameters: name with examples, type with complete enum values, balance with units and examples, and budget_id with default behavior. This adds significant value beyond the bare schema.

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 specific action ('Create a new account') and resource ('in a budget'), distinguishing it from sibling tools like get_accounts (read) or create_transaction (different resource). The verb+resource combination is precise and unambiguous.

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?

No guidance on when to use this tool versus alternatives is provided. While it's clear this creates accounts, there's no mention of prerequisites (e.g., budget must exist), constraints, or comparison to similar operations like updating existing accounts. The description only states what it does, not when to use it.

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