Amplitude

Amp Get Retention

amp_get_retention

Read-onlyIdempotent

Get user retention metrics for a cohort over time. Returns retention percentages by time period (e.g., day 1, day 7, day 30).

Input Schema

TableJSON Schema

Name	Required	Description
`re`	No	Retention type: "rolling" or "bracket" (default "rolling")
`end`	Yes	End date (YYYYMMDD)
`start`	Yes	Start date (YYYYMMDD)
`_apiKey`	Yes	Amplitude API key
`_secretKey`	Yes	Amplitude secret key

Output Schema

TableJSON Schema

Name	Required	Description	Default
`series`	No	Retention metrics by cohort

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "series": {
+      "description": "Retention metrics by cohort",
+      "items": {
+        "properties": {
+          "cohort_date": {
+            "description": "Cohort start date",
+            "type": "string"
+          },
+          "retention": {
+            "description": "Retention rates by period",
+            "items": {
+              "properties": {
+                "date": {
+                  "description": "Retention period date",
+                  "type": "string"
+                },
+                "retention_rate": {
+                  "description": "Percentage retained (0-100)",
+                  "type": "number"
+                }
+              },
+              "type": "object"
+            },
+            "type": "array"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026

addedInput schema / examples

Added value: +[
+  {
+    "_apiKey": "your-amplitude-api-key",
+    "_secretKey": "your-amplitude-secret-key",
+    "end": "20240228",
+    "start": "20240101"
+  },
+  {
+    "_apiKey": "your-amplitude-api-key",
+    "_secretKey": "your-amplitude-secret-key",
+    "end": "20240228",
+    "re": "bracket",
+    "start": "20240101"
+  }
+]

First observedApr 22, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already provide readOnlyHint and idempotentHint, so the description adds value by specifying the output format (retention percentages by time period). This goes beyond the annotations while staying consistent with them.

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?

The description is concise with two sentences: the first states the core purpose, the second clarifies the return format. No extraneous information, every word adds value.

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 existence of an output schema and full parameter documentation, the description is complete enough. It explains the return value (retention percentages) but could optionally mention the cohort definition or default period granularity.

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 adequately documents all 5 parameters. The description does not add any additional parameter-level details beyond what is in the schema, meeting the baseline expectation.

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?

The description uses a specific verb ('Get') and resource ('user retention metrics') and clearly states what is returned (retention percentages by time period). The tool's purpose is distinct from siblings like amp_get_active_users or amp_get_events, which focus on different metrics.

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?

The description implies usage for analyzing cohort retention over time but does not explicitly state when to use this tool versus alternatives (e.g., amp_get_active_users). No when-not or alternative tools are mentioned, leaving the context of use somewhat vague.

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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