The MongoDB MCP server provides three tools with explicit schema definitions and reasonable descriptions. All three tools have input schemas with typed properties and descriptions. However, there are notable gaps: (1) Missing output schemas, none of the three tools document their return types, which violates pattern:tool and makes it harder for LLMs to plan downstream operations. (2) Parameter descriptions are present but minimal (1-10 words each); they lack actionable context like format constraints, valid ranges, or dependency hints. (3) The 'sample' tool's count parameter has min/max constraints (1-10) in the schema, which is good, but the description doesn't reinforce these bounds in natural language. (4) No tool descriptions explain WHEN to use them vs alternatives or what state changes occur (all three are read-only, which should be called out explicitly). (5) Error handling is minimal, the code catches errors generically but doesn't return actionable guidance to the LLM. (6) Tool names are clear and verb-driven ('aggregate', 'explain', 'sample'), which is a strength. Overall, this is a functional but incomplete implementation, descriptions exist but lack depth, and critical output documentation is absent.

• Add output schema documentation to each tool. For 'aggregate', document: { documents: Array<Object>, iterationCount?: number }. For 'explain', document: { executionStats: {...}, executionStages: {...} }. For 'sample', document: { documents: Array<Object>, count: number }.
• Expand tool descriptions to 100-200 chars and include WHEN/WHY. E.g., 'aggregate: Run a MongoDB aggregation pipeline to transform, filter, and aggregate documents. Use this to compute statistics, group data, or filter large collections. Returns an array of result documents.'
• Replace example values in parameter descriptions with formal constraints. Instead of 'e.g., $match, $group, $sort', reference MongoDB aggregation pipeline documentation or provide an enum of common stages if feasible.
• Implement recovery guidance in error responses. When a collection is not found, catch the error and return: 'Collection not found. Available collections: [list]. Did you mean one of these?' This lets LLMs self-correct without an extra discovery call.
• Add tool annotations to the ListToolsRequestSchema response. Set readOnlyHint: true for all three tools, and idempotentHint: true for aggregate and explain (sample is idempotent too). Example: { name: 'aggregate', ..., readOnlyHint: true, idempotentHint: true }
• Enhance resource schema responses to include nullable status, min/max constraints, and sample values. E.g., { field_name: 'status', field_type: 'string', nullable: false, examples: ['active', 'inactive'], description: '...' }