Set or increment a custom metric value (e.g., +1) and retrieve the saved result to track analytics.
Set a custom metric to a value, or increment it with a + prefixed value (e.g. +1). Returns the saved value.
| Name | Required | Description | Default |
|---|---|---|---|
| value | Yes | target value (also accepts increments with a + prefix) | |
| metric | Yes | metric name |
| Name | Required | Description | Default |
|---|---|---|---|
| value | Yes | ||
| metric | Yes |
Changes observed during successful MCP inspections.
v2.0.0Output schema / properties / metric / descriptionRemoved value: -"metric name"Output schema / properties / value / descriptionRemoved value: -"saved value"v1.2.9v1.2.8Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": false,
+ "properties": {
+ "metric": {
+ "description": "metric name",
+ "type": "string"
+ },
+ "value": {
+ "description": "saved value",
+ "type": "string"
+ }
+ },
+ "required": [
+ "metric",
+ "value"
+ ],
+ "type": "object"
+}v1.1.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate this is a mutating, non-idempotent, non-destructive operation. The description adds meaningful behavioral nuance: the + prefix triggers incrementing rather than overwriting, and the saved value is returned. This goes beyond the annotations and helps the agent predict the outcome.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single, front-loaded sentence that efficiently conveys the operation, the increment variant, an example, and the return value. There is no filler or repetition of schema details.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's simplicity—two required parameters, full schema coverage, and an output schema—the description is largely complete. It explains both usage modes and the return value. A small gap is the absence of context about prerequisite setup or where custom metrics are scoped, but this is not critical for a basic call.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so both parameters are already documented in the schema. The description reinforces the value parameter's dual behavior with an example ('+1') but adds no new semantic information beyond what the schema states.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description uses specific verbs ('Set', 'increment') and identifies the resource ('custom metric'), clearly distinguishing this operation from sibling tools. It also states the two supported input modes and the return behavior, so an agent knows exactly what the tool does without inspecting the schema.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies when to use this tool—whenever a custom metric needs to be set or incremented—but it does not provide explicit guidance on when to prefer this over alternatives or when not to use it. No exclusions or alternative tool references are given.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.