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splitwise-mcp

by chrischall
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Remote

sw_create_expense

Create a Splitwise expense with equal or custom per-person splits. Confirm the preview before the expense is added to a group.

Instructions

Create a Splitwise expense. Use split_equally:true to split evenly among group members, or provide a users array for custom per-person splits (paid_share and owed_share as decimal strings like "25.00"). cost must be a decimal string. Asks the user to confirm first: a confirmation prompt where the client supports one; otherwise the first call returns a preview and a confirmToken, and only a repeat call with that token proceeds (see MCP_CONFIRM_MODE).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
costYesTotal cost as decimal string, e.g. "25.00"
dateNoISO 8601 datetime
usersNoCustom split (mutually exclusive with split_equally). Full list of participants required.
detailsNoNotes
group_idYesGroup to add expense to (use 0 for no group)
category_idNoCategory id from sw_get_categories
descriptionYesShort description of the expense
confirmTokenNoONLY for the two-step confirmation fallback (a client without MCP elicitation). The confirmToken from this same tool's phase-1 "confirmation-required" response, passed back ONLY after the user has seen that preview and explicitly approved it in chat — never on the first call, never invented, never reused. Call again with the same arguments. Ignored when the client supports elicitation.
currency_codeNoCurrency code, e.g. "USD". Defaults to group/user default.
split_equallyNoSplit equally among group members (mutually exclusive with users)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv3.2.0
    • removedInput schema / properties / confirm
      Removed value: -{
-  "description": "Must be true to proceed. Without this, the tool returns a preview.",
-  "type": "boolean"
-}
    • addedInput schema / properties / confirmToken
      Added value: +{
+  "description": "ONLY for the two-step confirmation fallback (a client without MCP elicitation). The confirmToken from this same tool's phase-1 \"confirmation-required\" response, passed back ONLY after the user has seen that preview and explicitly approved it in chat — never on the first call, never invented, never reused. Call again with the same arguments. Ignored when the client supports elicitation.",
+  "type": "string"
+}
  2. Changed1 schema field changedv3.0.0
    • changedInput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
  3. First observedv2.1.5

TDQS

A4.6/5.0
Behavior5/5

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

No annotations provided, so description carries full burden. It discloses the confirmation behavior in detail: first call returns preview and confirmToken, repeat call with token proceeds. Also notes that cost must be a decimal string. This is a key behavioral trait that an agent needs to know.

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

Conciseness4/5

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

Description is a single paragraph but well-organized: purpose, splitting options, cost format, and confirmation flow. It is information-dense without being verbose, and front-loads the core purpose before diving into details.

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

Completeness4/5

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

Given the tool's complexity (10 params, confirmation flow, no output schema), the description covers the essential behaviors: how to split, what to expect on confirmation, and the required format for cost. It lacks explicit mention of the return value (e.g., created expense ID), but this is commonly inferred for creation tools.

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

Parameters5/5

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

Schema coverage is 100%, but description adds critical semantics: explains the mutual exclusivity of split_equally and users, the decimal string format for shares, and the confirmToken usage. Provides context beyond schema descriptions, such as 'full list of participants required' for users array.

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?

States the specific verb 'Create' and resource 'Splitwise expense' clearly. Distinguishes from siblings like sw_update_expense and sw_delete_expense by the create action. Also clarifies the two splitting modes (equal vs custom) which is essential.

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

Usage Guidelines4/5

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

Clearly indicates when to use (creating an expense) and provides guidance on choosing between split_equally and users. Doesn't explicitly mention alternatives for updating or deleting, but the create context is unambiguous. Also explains the confirmation flow which is a usage condition.

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

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