Rahul D Sarker: Marketing & RevOps Tools

Retargeting Pool Size Estimator

retargeting_pool_size_estimator

Read-onlyIdempotent

Estimate the addressable retargeting pool from monthly visitors, window, and match rate, plus the budget needed to hit a target weekly frequency. See the full version at https://rahuldsarker.co/calculators/retargeting-pool-size-estimator

Input Schema

TableJSON Schema

Name	Required	Description
`cpm`	Yes	Retargeting CPM
`currency`	No	ISO 4217 code for money in the result, e.g. "USD", "INR", "EUR", "GBP". Omit to show plain numbers.
`visitors`	Yes	Monthly unique visitors
`targetFreq`	Yes	Target weekly impressions per user
`windowDays`	Yes	Retargeting window, in days
`matchRatePct`	Yes	Cookie / match rate, as a percentage

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

B3.4/5.0

Behavior3/5

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

Annotations already state readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds only the calculation scope and a link to a fuller version; it does not disclose assumptions, input limitations, auth needs, or rate behavior.

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?

Two tight sentences with no filler. The core estimate is front-loaded, the secondary budget output follows, and the link is deferred to the end.

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?

An output schema exists, so return values need not be explained, and the schema fully documents the six parameters. The description is complete enough for calling the tool, though it could note estimator assumptions or that currency is optional.

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 the schema carries the parameter documentation and the baseline is 3. The description maps "monthly visitors," "window," and "match rate" to inputs and mentions budget, but adds no syntax, unit clarification, or handling for the optional currency parameter.

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 ("Estimate") and resource ("addressable retargeting pool") and adds the secondary output ("budget needed to hit a target weekly frequency"). It is clear but does not explicitly distinguish itself from similar siblings like lookalike_audience_pool_calculator or total_addressable_market_estimator.

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

Usage Guidelines2/5

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

The description explains what the calculator computes but gives no when-to-use guidance, no conditions for choosing it over alternatives, and no exclusions. A user must infer its place from the name alone.

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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