MaCalculatriceEnLigne

calculate_churn_rate

Compute customer or revenue churn rate over a period. Use for SaaS retention analysis. Inputs: starting customers, churned, period length. Returns churn %, retention %, and annualized rate. See list_bundles for related 'finance-universal' calculators.

Input Schema

TableJSON Schema

Name	Required	Description
`period_months`	No	Period in months
`lost_customers`	Yes	Customers lost
`start_customers`	Yes	Customers at period start

Output Schema

TableJSON Schema

Name	Required	Description
`result`	No	Computed result. Object whose fields depend on the tool (e.g. {tax, marginal_rate, brackets} for tax tools, {volume_l, gallons} for volume tools).
`source`	No	Authoritative source for the rule or formula (e.g. "Article 197 CGI", "NF DTU 21").
`formula`	No	Human-readable formula or method used (e.g. "I=P·r·t", "Magnus formula").
`reference_url`	No	Link to a calcul2 page documenting the calculation in detail.

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 13, 2026

TDQS

A4.1/5.0

Behavior3/5

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

Describes inputs and outputs (churn %, retention %, annualized rate) but does not explicitly state that the tool performs a read-only computation without side effects. With no annotations, the description carries the burden but leaves ambiguity about mutability.

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, each contributing essential information: what it does, when to use, expected inputs, and outputs. Efficiently front-loaded.

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 simple calculation tool with complete schema descriptions and explicit mention of outputs, no additional context is needed. The description is fully sufficient.

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 has 100% description coverage for all three parameters, and the description only restates the inputs without adding new semantic meaning beyond what the schema provides.

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?

Clearly states the tool computes customer or revenue churn rate, specifies it's for SaaS retention analysis, and distinguishes itself from siblings by directing to list_bundles for related calculators.

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?

Provides clear context for when to use (SaaS retention analysis) and mentions list_bundles for related tools, but lacks explicit when-not-to-use instructions or direct alternatives.

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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