Unity MCP Pro shows moderate tool definition structure but falls well short of production quality. While all 19 tools have names and descriptions, critical gaps emerge: (1) Input schemas are present but lack depth, parameters have types and brief descriptions, but many lack constraints, enums, format specifications, or range limits; (2) No output schemas are documented anywhere, the response structure for each tool is opaque to LLMs, blocking composition and chaining; (3) Descriptions are sparse (many under 50 chars, well below the 194-char baseline); (4) No error handling guidance, tools do not explain what happens on failure, what to retry, or how to recover; (5) Parameter design is primitive, many accept free-form strings where enums would prevent hallucination (e.g., agent_type: 'Patrol'|'Chase'|'Wander', build profile names, schema type names); (6) Security gaps, sensitive file paths and project modification tools lack permission documentation or dry-run patterns; (7) Composition is weak, no evidence that tool outputs contain the IDs/references downstream tools need (e.g., does create_addressable_group return the group name for use by set_addressable_address?); (8) No pagination, rate limiting, or result capping, analysis tools like find_unused_assets could return thousands of items, breaking context windows. Most tools read bare-bones from Editor/Commands/*.cs with minimal introspection. This is typical of community MCP servers, functional but unoptimized for LLM reasoning.
No output schemas documented for any tool. LLMs cannot infer what fields a tool returns, blocking composition and chaining. E.g., does create_addressable_group return the group_id or group_name? Must use get_addressable_info as a follow-up discovery call.
Free-form string parameters lack enum constraints, inviting hallucinated values. agent_type accepts 'Patrol'|'Chase'|'Wander' but this is described in prose only, not constrained. build_addressables profile name is unconstrained. create_addressable_group schema type is unconstrained. LLMs will invent invalid values.
Recommendations
For each tool, add a 150 - 250 character description following this template: '[WHAT] This tool {verb}s {object}. [WHEN] Call it when {condition}. [WHAT IT RETURNS] It returns {structure}. [DEPS] Requires {prerequisites}.' Example: 'This tool creates a finite state machine script in the specified path. Call it first to set up AI behavior state management. Returns the script file path and initial state. Requires write access to the project folder.'
Document output schemas for all 19 tools. Use JSON Schema format in a structured section of the tool definition. Example for create_addressable_group: {"type": "object", "properties": {"group_id": {"type": "string"}, "group_name": {"type": "string"}, "schema": {"type": "string"}, "success": {"type": "boolean"}}}
Convert free-form string parameters to enums. For setup_ai_agent.agent_type, define enum: ["Patrol", "Chase", "Wander"]. For build_addressables.profile, document available profiles or add enum constraint. For create_addressable_group.schema, define enum: ["PackedAssets", "BundledAssets", etc.]
Add error handling guidance to each tool. E.g., 'If the script_path is invalid, returns error: "Invalid path, use relative paths like Assets/Scripts/AI". Retry with correct path format.' For each tool, document at least 2-3 common failure modes and recovery steps.
Add pagination to analysis tools. E.g., find_unused_assets should accept limit (1-100, default 20) and offset/cursor parameters. Return {"results": [...], "total": N, "next_cursor": "xyz" } so LLM can iterate.
Tool descriptions are universally terse (10-40 chars), far below the 194-char production baseline. E.g., 'Get information about addressable assets and groups' (54 chars) does not explain WHEN to call it vs analyze_addressables, WHAT structure it returns, or WHAT parameters filter results. LLMs cannot distinguish similar tools.
No error handling guidance. Tools do not document what happens on failure (e.g., file not found, permission denied, invalid path). No recovery suggestions. LLMs receive bare errors with no actionable next step.
Analysis tools (find_unused_assets, analyze_scripts, get_asset_dependencies) have no pagination, limits, or result capping. A large project could return thousands of results, exploding context window. No mention of max result count or cursor-based pagination.
Destructive tools (create_*, set_*, build_*) lack dry-run or confirmation patterns. An LLM could inadvertently create duplicate state machines or overwrite addressable groups. No permission gates documented.
Parameter descriptions lack specificity. 'Path where the state machine script will be created' does not specify format (absolute vs relative, Unix vs Windows), constraints (max length, allowed characters), or examples. Ambiguity invites LLM errors.
No evidence tool outputs include chaining IDs. E.g., does create_addressable_group return group_id, group_name, or both? Must downstream tool set_addressable_address receive the output directly, or must LLM make separate lookup calls?
No scope or permission declarations. E.g., setup_ai_agent modifies the active Unity scene, what permissions are required? Can any user/agent run this, or is it restricted? No audit trail guidance.
Add dry-run or confirmation parameters to destructive tools. E.g., build_addressables should accept dry_run: bool. If true, simulate build and return what would change without committing. Or require explicit confirm=true parameter for write operations.
Add scope/permission annotations to tool descriptions. E.g., 'Requires write:project and admin:addressables scope.' State which user groups can invoke the tool.
Ensure tool output includes chaining IDs. When create_addressable_group succeeds, return both group_id and group_name so LLM can pass output to set_addressable_address without extra lookup. Test tool chains end-to-end.
Add constraints to numeric and string parameters. E.g., waypoint_count: {"type": "integer", "minimum": 1, "maximum": 1000, "description": "Number of waypoints (1-1000, typically 5-20)"} to prevent absurd values.
Document idempotency. Which tools are safe to retry? E.g., if set_addressable_address fails mid-execution, is it safe to re-run with the same address? Add idempotent:true annotation if applicable, or explain retry behavior.