YNAB MCP Server

Execute YNAB Tool

ynab_tool_execute

Read-onlyIdempotent

Execute read-only YNAB tools by name with JSON input. Discover available tools first, then run queries like transactions, categories, and payees.

Instructions

Execute an existing read-only YNAB MCP tool by name. Use ynab_tool_index first to discover YNAB tool names, then pass the selected tool_name and its JSON input. Write-capable tools must be called directly or through ynab_write_tool_execute when YNAB_ALLOW_WRITES=1.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`input`	No	JSON input for the selected YNAB tool. Omit or pass an empty object for tools that take no input.
`tool_name`	Yes	Existing read-only YNAB tool name, such as review_unapproved, get_transactions, list_categories, search_categories, or search_payees.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv5.4.0Sep 15, 2026
- removedOutput schema / properties / result / description
```
Removed value: -"Structured result returned by Execute YNAB Tool."
```

Changed1 schema field changedv5.1.1Jul 21, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "result": {
+      "description": "Structured result returned by Execute YNAB Tool."
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "type": "object"
+}

Addedv3.1.0Jul 5, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, and the description reinforces the read-only boundary while adding the routing behavior and the YNAB_ALLOW_WRITES condition. It does not describe failure behavior, but the output schema and annotations cover the main safety contract, so this is solid rather than exceptional.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences with the core purpose first, then the usage workflow, then the write-tool exception. Every sentence earns its place and no words are wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a generic dispatcher, the description covers discovery, parameter passing, the read-only restriction, and the alternative path for write tools. With output schema and rich annotations present, nothing essential is missing for an agent to select and invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the schema already documents tool_name with examples and input and describes input as an optional JSON object. The description adds workflow context (use index first) but no additional parameter semantics beyond what the schema provides, making baseline 3 appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific action—'Execute an existing read-only YNAB MCP tool by name'—and immediately separates this dispatcher from ynab_tool_index (discovery) and from direct write tools. This gives an agent a clear model of what the tool does and what it is not.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly tells the agent to call ynab_tool_index first, then pass tool_name and JSON input, and it names the alternative path for write-capable tools (direct call or ynab_write_tool_execute when YNAB_ALLOW_WRITES=1). This is concrete when-to-use and when-not-to-use guidance.

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