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Model Context Protocol inspector - a tool for inspecting and testing MCP servers with CLI, client, and server components
MCP Inspector provides 8 tools for introspection and control of connected MCP servers. However, the server has significant definition quality issues: most tool descriptions are extremely brief (10-30 chars, well below the 50-200 char baseline for LLM optimization), several critical tools lack visible input schema definitions in the provided source, and parameter descriptions are missing or minimal. Tools are well-named (verb_noun pattern) and cover a coherent set of capabilities (list/read resources, prompts, tools; set logging). However, the lack of documented output schemas, missing parameter descriptions, and absence of error handling guidance severely limits LLM usability. The server appears designed as an inspector/debugger rather than a production agent tool, which explains the lean definitions, but even inspector tools benefit from richer descriptions to guide tool selection.
Set the logging level for the connected MCP server
Get a prompt by name with optional arguments
List all available prompts from the connected MCP server
List all available resources from the connected MCP server
Read a resource by URI
List all available resource templates from the connected MCP server
Call a tool by name with specified arguments
Tool descriptions are critically short (10-35 chars), far below the 50-200 char baseline for LLM-optimized descriptions. Examples: 'List all available tools from the connected MCP server' (54 chars, borderline); 'List all available resources' (28 chars, too brief). Short descriptions lack context for when/why to use each tool and prevent LLMs from distinguishing similar tools (e.g., tools/list vs resources/list vs prompts/list).
Output schemas are not documented. Tools like tools/list, resources/list, resources/templates/list, and prompts/list do not show what fields they return. LLMs cannot plan downstream tool calls or extract required IDs (e.g., does tools/list return tool_id, name, description? what fields?). This violates the pattern requirement that documented return types are essential for agent composition.
Inferred effective spec: 2025-06-18+.
| Scored | Grade | Overall | Spec posture | Rubric |
|---|---|---|---|---|
| 2026-09-22 | D | 50 | 2025-06-18+ | v2 |
| 2026-03-09 | F | 30 | - | v1 |
List all available tools from the connected MCP server
Parameter descriptions are missing or minimal. 'tools/call' has input schema with 'name' and 'arguments' parameters, but no descriptions explain what structure 'arguments' should have, what happens if arguments are malformed, or how to obtain valid tool names. 'prompts/get' similarly lacks parameter detail. Per the rubric, 100% of A+ tool params must have descriptions.
No error handling guidance. Tools do not document what errors may occur, when they are retryable, or what the LLM should do next. For example, if 'tools/call' fails because a tool doesn't exist, should the LLM retry, call tools/list first, or report to the user? No recovery guidance is provided.
logging/setLevel tool represents a deprecated pattern. The 'Logging' feature and logging/setLevel tool were removed from the MCP spec as of 2026-07-28. This tool should be replaced with stderr logging or OpenTelemetry instrumentation for better spec alignment.
No tool annotations. Tools lack readOnlyHint, destructiveHint, or idempotentHint annotations. While most tools are read-only (tools/list, resources/list, etc.), the absence of annotations means LLMs cannot determine call safety or retry behavior without reading descriptions. tools/call and logging/setLevel are write operations, marking them with destructiveHint or appropriate annotations would clarify intent.