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Mercado Livre MCP Server

by newerton

Mercado Livre - MCP Server

This project is part of the Model Context Protocol (MCP) ecosystem and provides tools for integrating with external sources and managing specific domain models. It is designed to demonstrate how to build an MCP server that scrapes products from Mercado Livre, with strong data validation to ensure reliability.

Table of Contents

Related MCP server: Investidor10 MCP Server

Features

  • get-produtos: Fetch basic product information.

  • Input validation using Zod.

  • Integration with the Mercado Livre API using fetch (infrastructure layer).

Architecture

The project follows a layered architecture inspired by Domain-Driven Design (DDD) patterns:

  • Domain (src/domain): Defines interfaces and types that represent data structures (e.g., Mercado Livre).

  • Infrastructure (src/infrastructure): Implements external services, such as MercadoLivreApiService, responsible for making HTTP calls to the Mercado Livre API.

  • Application (src/application): Contains business logic in MercadoLivreService, which processes and formats data from the infrastructure.

  • Interface (src/interface): Includes controllers (MercadoLivreToolsController) that register tools in the MCP server, define validation schemas, and return results.

  • Entry Point (src/main.ts): Initializes the McpServer, configures the transport (StdioServerTransport), instantiates services and controllers, and starts listening on stdio.

The folder structure is as follows:

src/
├── domain/
│   └── models/           # Domain interfaces
├── infrastructure/
│   └── services/         # External API implementations (Mercado Livre)
├── application/
│   └── services/         # Business logic and data formatting
├── interface/
│   └── controllers/      # MCP tool registration and validation
└── main.ts               # Server entry point
build/                    # Compiled JavaScript code
.vscode/                  # Contains the mcp.json file, MCP Server config

Installation

git clone git@github.com:newerton/mcp-mercado-livre.git
cd mcp-mercado-livre
npm install
npm run build

MCP Server Configuration in VSCode

  1. Press Ctrl+Shift+P and select "MCP: List Servers"

  2. Select "products" and then "Start Server"

MCP Server Output in VSCode

  1. Press Ctrl+Shift+P and select "MCP: List Servers"

  2. Select "products" and then "Show Output"

Contribution

Pull requests are welcome! Feel free to open issues and discuss improvements.

License

This project is licensed under the MIT license - see the LICENSE file for details.

Available Tools

1 tool
get-produtosC

Buscar informações básicas de produtos

ParametersJSON Schema
NameRequiredDescriptionDefault
productsYesArray of product names

TDQS

C2.6/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full burden. It states the tool searches for basic product information, but doesn't disclose behavioral traits like whether it's read-only, requires authentication, has rate limits, or what happens with invalid inputs. This leaves significant gaps in understanding how the tool behaves.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence in Portuguese ('Buscar informações básicas de produtos') that's appropriately sized and front-loaded. There's no wasted text, though it could be slightly more informative without losing conciseness.

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

Completeness2/5

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

Given no annotations, no output schema, and a simple input schema, the description is incomplete. It doesn't explain what 'basic information' includes, how results are returned, or any error handling, making it inadequate for a tool that presumably returns data based on product names.

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?

The input schema has 100% description coverage, with the 'products' parameter documented as 'Array of product names'. The description adds no additional meaning beyond this, so it meets the baseline of 3 where the schema does the heavy lifting, but doesn't compensate or enhance parameter understanding.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose3/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description 'Buscar informações básicas de produtos' (Search for basic product information) states a clear verb ('Buscar') and resource ('produtos'), but it's vague about what constitutes 'basic information' and doesn't specify scope or format. Without sibling tools, differentiation isn't needed, but the purpose remains somewhat ambiguous.

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

Usage Guidelines2/5

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

No guidance is provided on when to use this tool—there's no mention of prerequisites, alternatives, or specific contexts. The description implies it's for searching product info, but offers no further usage instructions, leaving the agent to infer appropriate scenarios.

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

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 1 tool update
    • First observedget-produtos

TDQS

C2.8/5.0

Scored across 1 tool

Disambiguation5/5

With only one tool, there is no possibility of confusion or overlap between tools. The tool has a clear and distinct purpose, making disambiguation trivial.

Naming Consistency5/5

The single tool name follows a consistent verb-noun pattern (get-produtos), and with no other tools to compare, there is no inconsistency in naming conventions.

Tool Count2/5

One tool is too few for a server named 'Mercado Livre MCP Server', which suggests a marketplace domain. This minimal set likely leaves significant gaps in functionality, such as creating, updating, or deleting products, or handling orders and users.

Completeness1/5

The tool surface is severely incomplete for a marketplace server. It only provides basic product information retrieval, missing essential operations like product creation, updates, order management, and user interactions, which are critical for such a domain.

Maintenance

ActivityMaintained
ResponsivenessUnresponsive

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