Model Context Protocol inspector - a tool for inspecting and testing MCP servers with CLI, client, and server components
MCP Inspector exposes 8 tools with clear verb-noun naming (listTools, callTool, readResource, etc.). All tools have descriptions (avg ~60 chars, baseline 194 chars). Input schemas are present and typed for all tools. However, descriptions are significantly shorter than production baselines and lack context on WHEN to use each tool or what downstream actions they enable. Parameter descriptions are minimal (e.g., 'Arguments to pass to the tool' for callTool.args is generic). No output schemas documented. Error handling is basic, no recovery guidance or actionable error messages visible in the code. The server is a meta-tool for inspecting other MCP servers, which limits the need for complex composition, but descriptions should still guide LLM selection and explain dependencies.
Call a tool on the connected MCP server with specified arguments
Get a specific prompt from the connected MCP server with optional arguments
List all available prompts from the connected MCP server
List all available resource templates from the connected MCP server
List all available resources from the connected MCP server
List all available tools from the connected MCP server
Read the content of a specific resource from the connected MCP server
Set the logging level for the connected MCP server
Parameter descriptions are generic and lack actionable detail. 'Arguments to pass to the tool' (callTool.args) and 'Optional arguments for the prompt' (getPrompt.args) do not explain format, constraints, or examples. LLMs cannot infer valid input structure.
Tool descriptions are 40 - 60 characters, well below the 194-char production baseline. Descriptions lack context on WHEN to use each tool, what it returns, or how it chains with others. E.g., 'List all available tools from the connected MCP server' does not explain that this is a discovery step before callTool.
No output schemas documented. LLMs cannot plan downstream tool calls or extract required fields (e.g., tool names from listTools, resource URIs from listResources). This forces agents to guess response structure.
Inferred effective spec: <=2025-11-25.
| Scored | Grade | Overall | Spec posture | Rubric |
|---|---|---|---|---|
| 2026-09-23 | D | 58 | <=2025-11-25 | v2 |
callTool accepts 'args' as a free-form object with no schema constraints. LLMs cannot validate argument structure before calling. No guidance on required vs optional fields, types, or error recovery if arguments are malformed.
setLoggingLevel accepts 'level' as a string but does not enforce an enum. Description lists valid values ('debug, info, notice, warning, error, alert, emergency') as text, not as a formal constraint. LLMs may hallucinate invalid levels.