ChurnLens

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io.github.kindrat86/churnlensv1.0.1

Buyer-side SaaS due-diligence maths: NRR, GRR, revenue concentration, zombie MRR, LTV:CAC.

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analyze_revenue_concentration

Assess customer concentration risk across a book of revenue using the Herfindahl-Hirschman Index (HHI), top-N share and whale detection. Answers the question every acquirer asks first: how much revenue walks out with one logo?

customer_mrrsarray, required

Per-customer MRR values. Order does not matter.

top_nnumber

How many top customers to aggregate for the top-N share. Default 5.

whale_threshold_pctnumber

Revenue share above which a customer counts as a whale. Default 25.

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Tools (6)

analyze_revenue_concentration

Argument	Type	Description
top_n	number	How many top customers to aggregate for the top-N share. Default 5.
customer_mrrs*	array	Per-customer MRR values. Order does not matter.
whale_threshold_pct	number	Revenue share above which a customer counts as a whale. Default 25.

Input schema (JSON)

{
  "type": "object",
  "required": [
    "customer_mrrs"
  ],
  "properties": {
    "top_n": {
      "type": "number",
      "description": "How many top customers to aggregate for the top-N share. Default 5."
    },
    "customer_mrrs": {
      "type": "array",
      "items": {
        "type": "number"
      },
      "description": "Per-customer MRR values. Order does not matter."
    },
    "whale_threshold_pct": {
      "type": "number",
      "description": "Revenue share above which a customer counts as a whale. Default 25."
    }
  }
}

calculate_churn_rate

Calculate net revenue retention (NRR), gross revenue retention (GRR), revenue churn and implied customer lifetime from one period's MRR movements. Also reports the NRR-minus-GRR spread, which reveals how much churn is being masked by expansion revenue.

Argument	Type	Description
churned_mrr	number	MRR lost to full cancellations.
starting_mrr*	number	MRR at the start of the period, in any single currency unit.
expansion_mrr	number	MRR gained from upgrades and expansion within the existing base. Excludes new customers.
contraction_mrr	number	MRR lost to downgrades (customer retained).

Input schema (JSON)

{
  "type": "object",
  "required": [
    "starting_mrr"
  ],
  "properties": {
    "churned_mrr": {
      "type": "number",
      "description": "MRR lost to full cancellations."
    },
    "starting_mrr": {
      "type": "number",
      "description": "MRR at the start of the period, in any single currency unit."
    },
    "expansion_mrr": {
      "type": "number",
      "description": "MRR gained from upgrades and expansion within the existing base. Excludes new customers."
    },
    "contraction_mrr": {
      "type": "number",
      "description": "MRR lost to downgrades (customer retained)."
    }
  }
}

calculate_ltv

Calculate gross-margin-adjusted customer lifetime value, the LTV:CAC ratio and CAC payback in months. Omitting gross margin yields lifetime revenue rather than lifetime value — usually a third of the number.

Argument	Type	Description
cac	number	Customer acquisition cost. Optional — supply it to get the ratio and payback.
arpa*	number	Average revenue per account, per month.
gross_margin_pct	number	Gross margin percentage. Defaults to 100, which gives lifetime revenue.
monthly_churn_rate_pct*	number	Monthly churn, as a percentage.

Input schema (JSON)

{
  "type": "object",
  "required": [
    "arpa",
    "monthly_churn_rate_pct"
  ],
  "properties": {
    "cac": {
      "type": "number",
      "description": "Customer acquisition cost. Optional — supply it to get the ratio and payback."
    },
    "arpa": {
      "type": "number",
      "description": "Average revenue per account, per month."
    },
    "gross_margin_pct": {
      "type": "number",
      "description": "Gross margin percentage. Defaults to 100, which gives lifetime revenue."
    },
    "monthly_churn_rate_pct": {
      "type": "number",
      "description": "Monthly churn, as a percentage."
    }
  }
}

detect_zombie_mrr

Identify dormant-but-paying accounts — revenue that still counts in MRR but whose customers have stopped showing up. Zombie revenue is one renewal notice from cancelling and is invisible to standard revenue dashboards.

Argument	Type	Description
accounts*	array	One entry per paying account.
threshold_days	number	Days of inactivity before an account counts as dormant. Default 90.

Input schema (JSON)

{
  "type": "object",
  "required": [
    "accounts"
  ],
  "properties": {
    "accounts": {
      "type": "array",
      "items": {
        "type": "object",
        "required": [
          "mrr",
          "days_since_last_activity"
        ],
        "properties": {
          "mrr": {
            "type": "number"
          },
          "customer": {
            "type": "string"
          },
          "days_since_last_activity": {
            "type": "number"
          }
        }
      },
      "description": "One entry per paying account."
    },
    "threshold_days": {
      "type": "number",
      "description": "Days of inactivity before an account counts as dormant. Default 90."
    }
  }
}

get_scoring_bands

Return the scoring thresholds ChurnLens applies to NRR, revenue concentration and the composite health score. These are bands, not measured benchmark data — the sourced benchmark figures are cited at https://churnlens.site/benchmarks.

Argument	Type	Description
metric	string	Which band set to return: 'nrr', 'concentration', 'health', or omit for all.

Input schema (JSON)

{
  "type": "object",
  "properties": {
    "metric": {
      "enum": [
        "nrr",
        "concentration",
        "health"
      ],
      "type": "string",
      "description": "Which band set to return: 'nrr', 'concentration', 'health', or omit for all."
    }
  }
}

score_saas_health

Score a SaaS business 0-100 across five dimensions — retention, growth, concentration, efficiency and durability — and return the composite. Every mapping is published, so the score can be reconstructed by hand.

Argument	Type	Description
nrr_pct*	number	Net revenue retention, as a percentage.
ltv_to_cac_ratio*	number	Lifetime value divided by customer acquisition cost.
annual_plan_share_pct*	number	Share of revenue on annual contracts, as a percentage.
monthly_churn_rate_pct*	number	Monthly revenue churn, as a percentage (5 means 5%).
top_customer_share_pct*	number	Largest single customer's share of revenue, as a percentage.

Input schema (JSON)

{
  "type": "object",
  "required": [
    "monthly_churn_rate_pct",
    "nrr_pct",
    "top_customer_share_pct",
    "ltv_to_cac_ratio",
    "annual_plan_share_pct"
  ],
  "properties": {
    "nrr_pct": {
      "type": "number",
      "description": "Net revenue retention, as a percentage."
    },
    "ltv_to_cac_ratio": {
      "type": "number",
      "description": "Lifetime value divided by customer acquisition cost."
    },
    "annual_plan_share_pct": {
      "type": "number",
      "description": "Share of revenue on annual contracts, as a percentage."
    },
    "monthly_churn_rate_pct": {
      "type": "number",
      "description": "Monthly revenue churn, as a percentage (5 means 5%)."
    },
    "top_customer_share_pct": {
      "type": "number",
      "description": "Largest single customer's share of revenue, as a percentage."
    }
  }
}