Letter IRL

Save return address

set_return_address

DestructiveIdempotent

Save your preferred return address for future letters and postcards. The address is validated before saving, corrected when possible, and used automatically when you omit a sender address. U.S. addresses only.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "name": "<name>",
      "addressLine1": "<addressLine1>",
      "city": "<city>",
      "state": "<state>",
      "postalCode": "<postalCode>"
    },
    "name": "set_return_address"
  }
}

Input Schema

Name	Required	Description	Default
`city`	Yes
`name`	Yes
`state`	Yes
`country`	No
`postalCode`	Yes
`addressLine1`	Yes
`addressLine2`	No

Output Schema

Name	Required	Description	Default
`errors`	No
`address`	No
`message`	Yes
`success`	Yes
`wasAutoCorrected`	Yes
`correctionDetails`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 7, 2026

TDQS

A4/5.0

Behavior4/5

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

Beyond the annotations, the description discloses that the address is validated before saving, corrected when possible, used automatically as a default sender address, and limited to U.S. addresses. It does not explicitly state that saving replaces an existing preferred address, despite destructiveHint being true, so the overwrite behavior remains implicit.

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 three tight sentences with no filler. It front-loads the core action and then adds the most relevant behavioral constraints.

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

Completeness3/5

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

The description adequately covers purpose, usage context, validation behavior, and country scope, and an output schema exists so return values need not be explained. However, for a seven-parameter tool with 0% schema description coverage, it leaves required input formats such as state abbreviations and postal code structure undocumented.

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

Parameters2/5

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

Schema description coverage is 0% across seven parameters, including five required fields, so the description carries the full burden of explaining them. It only adds the U.S.-only restriction and does not explain name, addressLine1, addressLine2, city, state, postalCode, or country expectations or formats.

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 and resource: 'Save your preferred return address for future letters and postcards.' It clearly distinguishes this from get_return_address and clear_return_address by focusing on saving the preferred address.

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

Usage Guidelines4/5

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

The description gives clear context for use: it saves a return address for future mail and is used automatically when no sender address is supplied. It also states the U.S.-only restriction, but it does not explicitly name when to use get_return_address or clear_return_address instead.

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

All Letter IRL tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

Resources

Need Help?