Postcodes

Random Postcode

random_postcode

Read-onlyIdempotent

Get a random valid UK postcode with full geographic details. Returns coordinates, region, district, ward, and constituency.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "random_postcode"
  }
}

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description
`lat`	No	Latitude coordinate
`lon`	No	Longitude coordinate
`codes`	Yes	Codes mapping object
`incode`	Yes	Incode part of postcode
`region`	No	Region name
`country`	Yes	Country name
`outcode`	Yes	Outcode part of postcode
`eastings`	No	Eastings grid reference
`postcode`	Yes	The UK postcode
`northings`	No	Northings grid reference
`admin_ward`	No	Administrative ward
`admin_district`	No	Administrative district
`parliamentary_constituency`	No	Parliamentary constituency

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "admin_district": {
+      "description": "Administrative district",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "admin_ward": {
+      "description": "Administrative ward",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "codes": {
+      "description": "Codes mapping object",
+      "type": "object"
+    },
+    "country": {
+      "description": "Country name",
+      "type": "string"
+    },
+    "eastings": {
+      "description": "Eastings grid reference",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "incode": {
+      "description": "Incode part of postcode",
+      "type": "string"
+    },
+    "lat": {
+      "description": "Latitude coordinate",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "lon": {
+      "description": "Longitude coordinate",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "northings": {
+      "description": "Northings grid reference",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "outcode": {
+      "description": "Outcode part of postcode",
+      "type": "string"
+    },
+    "parliamentary_constituency": {
+      "description": "Parliamentary constituency",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "postcode": {
+      "description": "The UK postcode",
+      "type": "string"
+    },
+    "region": {
+      "description": "Region name",
+      "type": [
+        "string",
+        "null"
+      ]
+    }
+  },
+  "required": [
+    "postcode",
+    "incode",
+    "outcode",
+    "country",
+    "codes"
+  ],
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026
- addedInput schema / examples
```
Added value: +[
+  {}
+]
```
First observedApr 14, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds useful context by specifying that the postcode is random and valid, and lists the returned geographic details, which goes beyond the annotations. It does not disclose additional limitations or caveats, but the positive annotation profile lowers the burden.

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 a single, front-loaded sentence that states the main purpose and then enumerates the returned data fields. There is no wasted wording, and the structure is easy to scan.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool is simple with 0 params and has a strong annotation profile. The description covers the core function (random valid UK postcode) and the key outputs (coordinates, region, etc.), which, combined with the output schema, offers a complete picture for an agent to invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has zero parameters, and schema coverage is trivially 100%. With 0 params, the baseline is 4, and the description appropriately omits parameter details since none exist. It adds nothing about parameters, but nothing is needed.

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 clearly states the action ('Get a random valid UK postcode') and highlights it returns full geographic details like coordinates, region, district, ward, and constituency. This distinguishes it from sibling tools such as lookup_postcode or validate_postcode, which serve different purposes.

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 the tool is for obtaining a random postcode rather than a specific one, but it does not explicitly state when to use this tool versus alternatives, nor does it mention any exclusions. Given the sibling names, an agent could infer the use case, but the guidance is not explicit.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Postcodes tools Inspect

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