postcardbot-mcp-server

send_postcard

Send physical postcards worldwide by providing an image URL and message. The tool prints and mails cards to real addresses using prepaid balance with volume-based pricing.

Instructions

Send a physical postcard that will be printed and mailed to a real address. Price depends on volume tier based on lifetime top-up (from $0.72–$1.99 USA, $1.99–$2.99 international). Charged from the user's prepaid Postcard.bot balance. Use check_balance to see current pricing tier before sending. Requires an image URL (publicly accessible) and a message (max 350 characters).

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": {
      "to": "<to>",
      "from": "<from>",
      "message": "<message>",
      "image_url": "<image_url>"
    },
    "name": "send_postcard"
  }
}

Input Schema

Name	Required	Description
`to`	Yes	Recipient (mailing) address
`from`	Yes	Sender (return) address
`message`	Yes	Message text for the back of the postcard (max 350 characters)
`image_url`	Yes	URL of the image for the front of the postcard. Must be a publicly accessible HTTPS URL. Recommended minimum resolution: 1875x1275 pixels.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.1.0Mar 8, 2026

TDQS

A4.4/5.0

Behavior4/5

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

With no annotations provided, the description carries full burden and does well by disclosing key behavioral traits: cost implications ('Price depends on volume tier... Charged from the user's prepaid Postcard.bot balance'), operational constraints ('printed and mailed to a real address'), and technical requirements ('publicly accessible HTTPS URL'). It doesn't mention delivery timeframes or error handling, keeping it from a perfect score.

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?

Front-loaded with core purpose, followed by cost, payment method, prerequisite, and requirements. Every sentence earns its place with zero waste, efficiently covering key aspects in a compact format.

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 no annotations and no output schema, the description does well by covering purpose, cost, payment, prerequisites, and key requirements. However, it lacks details on return values (e.g., confirmation ID, estimated delivery) and error cases, which would be helpful for a transactional tool with financial implications.

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 baseline is 3. The description adds minimal value beyond the schema: it mentions 'image URL (publicly accessible)' and 'message (max 350 characters)', which are already documented in the schema. No additional syntax or format details are provided.

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 specific action ('Send a physical postcard'), resource ('postcard'), and scope ('printed and mailed to a real address'). It distinguishes from siblings like 'bulk_send' by focusing on single sends, 'check_balance' by being a transactional tool, and 'check_status/get_pricing' by being an execution tool rather than informational.

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

Usage Guidelines5/5

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

Explicitly states when to use ('Use check_balance to see current pricing tier before sending') and provides clear prerequisites ('Requires an image URL... and a message...'). It also implies when not to use by specifying single-send context versus bulk operations.

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

Deploy Server