Rahul D Sarker: Marketing & RevOps Tools

MRR to ARR Calculator

mrr_to_arr_calculator

Read-onlyIdempotent

Annualize MRR into ARR, with an optional 12-month projection from expected net-new monthly revenue. See the full version at https://rahuldsarker.co/calculators/mrr-to-arr-calculator

Input Schema

TableJSON Schema

Name	Required	Description
`mrr`	Yes	Current monthly recurring revenue (MRR)
`currency`	No	ISO 4217 code for money in the result, e.g. "USD", "INR", "EUR", "GBP". Omit to show plain numbers.
`monthlyChurnAndContraction`	No	Expected monthly dollars lost to churn and contraction, optional, defaults to 0
`monthlyExpansionAndNewBusiness`	No	Expected monthly dollars added from new business plus expansion, optional, defaults to 0

Output Schema

TableJSON Schema

Name	Required	Description
`url`	Yes
`kind`	Yes
`tool`	Yes	The calculator tool that produced this result
`notes`	Yes
`title`	Yes
`inputs`	Yes
`compact`	Yes
`metrics`	Yes	Every "Label: value" line of the result; value is the first number on the line
`currency`	Yes
`benchmarks`	Yes	Rule-of-thumb verdicts for the headline numbers
`bookingUrl`	Yes
`calculator`	Yes	Slug of the interactive calculator on rahuldsarker.co

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 30, 2026

addedInput schema / properties / currency

Added value: +{
+  "description": "ISO 4217 code for money in the result, e.g. \"USD\", \"INR\", \"EUR\", \"GBP\". Omit to show plain numbers.",
+  "pattern": "^[A-Za-z]{3}$",
+  "type": "string"
+}

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "additionalProperties": false,
+  "properties": {
+    "benchmarks": {
+      "description": "Rule-of-thumb verdicts for the headline numbers",
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "band": {
+            "type": "string"
+          },
+          "display": {
+            "type": "string"
+          },
+          "metric": {
+            "type": "string"
+          },
+          "name": {
+            "type": "string"
+          },
+          "read": {
+            "type": "string"
+          },
+          "segment": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "source": {
+            "type": "string"
+          },
+          "target": {
+            "type": "string"
+          },
+          "tone": {
+            "enum": [
+              "good",
+              "ok",
+              "warn",
+              "bad"
+            ],
+            "type": "string"
+          },
+          "value": {
+            "type": "number"
+          }
+        },
+        "required": [
+          "metric",
+          "name",
+          "value",
+          "display",
+          "band",
+          "tone",
+          "read",
+          "target",
+          "segment",
+          "source"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "bookingUrl": {
+      "type": "string"
+    },
+    "calculator": {
+      "description": "Slug of the interactive calculator on rahuldsarker.co",
+      "type": "string"
+    },
+    "compact": {
+      "type": "boolean"
+    },
+    "currency": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "inputs": {
+      "additionalProperties": {},
+      "propertyNames": {
+        "type": "string"
+      },
+      "type": "object"
+    },
+    "kind": {
+      "const": "calculator",
+      "type": "string"
+    },
+    "metrics": {
+      "description": "Every \"Label: value\" line of the result; value is the first number on the line",
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "display": {
+            "type": "string"
+          },
+          "label": {
+            "type": "string"
+          },
+          "unit": {
+            "anyOf": [
+              {
+                "enum": [
+                  "currency",
+                  "x",
+                  "%",
+                  "months"
+                ],
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ]
+          },
+          "value": {
+            "type": [
+              "number",
+              "null"
+            ]
+          }
+        },
+        "required": [
+          "label",
+          "value",
+          "unit",
+          "display"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "notes": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "title": {
+      "type": "string"
+    },
+    "tool": {
+      "description": "The calculator tool that produced this result",
+      "type": "string"
+    },
+    "url": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "kind",
+    "tool",
+    "title",
+    "calculator",
+    "url",
+    "bookingUrl",
+    "currency",
+    "compact",
+    "inputs",
+    "metrics",
+    "notes",
+    "benchmarks"
+  ],
+  "type": "object"
+}

First observedSep 29, 2026

TDQS

A3.5/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is fully covered. The description adds the behavioral note that the projection is driven by expected net-new monthly revenue, but says nothing about how churn/contraction affects the projection or about output shape, leaving gaps beyond the annotation baseline.

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?

Two compact clauses that front-load the core operation before the optional extension. The trailing marketing URL adds no call-time value and is the one element that does not earn its place.

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?

The tool is a simple single-purpose calculator with full schema coverage, rich annotations, and an output schema, so little is left for the description to carry. It adequately covers the primary and optional modes, with only a minor gap around how the churn/expansion parameters shape the projection.

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 description coverage is 100%, so all four parameters are self-documenting; baseline is 3. The description restates the projection input in prose but adds no syntax, bounds, or interaction detail (e.g., how churn and expansion combine) beyond what the schema already provides.

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

Purpose4/5

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

States a specific verb+resource ('Annualize MRR into ARR') and adds a distinct secondary capability (optional 12-month projection). This distinguishes it from similarly-named siblings like arr_multiple_calculator and mrr_bridge_planner, though it never names or contrasts with them explicitly.

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

Usage Guidelines3/5

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

Usage is implied by the purpose: feed in MRR to get ARR, optionally enable the projection. There is no statement of when to prefer this over sibling revenue calculators, nor any prerequisites or exclusions, so the agent must infer scope.

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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