open_game

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

Goes well beyond the annotations by disclosing that switching games resets the session and safely unloads an already-injected runtime — a real side effect an agent must know about. It also explains caching behavior and the reused=true fast path, matching the idempotentHint while adding actionable detail on when a rebuild does or does not occur.

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

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

Front-loaded with the core action and session-role statement, then organized into engine bullets, repeat-call note, Args, and Returns. It is somewhat long and the Returns block lists a raw dict shape, but each section carries distinct information without filler.

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

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

With no output schema, the description supplies the return shape (ok, engine, metadata_path, index counts, elapsed, reused). Combined with engine support notes and the pointer to get_diagnostics for UE capabilities, an agent has everything needed to call this correctly and interpret the result.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, and the description fully compensates: game_dir as the recommended entry, metadata_path for nonstandard layouts with per-engine file names, engine for forced override ('generally not needed'), cache_dir's default of ~/.gamemod/cache, and force_rebuild's trigger condition. Every one of the five parameters gains meaning not present in the schema.

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

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

Opens with a specific verb+resource: selects a game and builds (or reuses) its metadata index, with cross-engine auto-detection spelled out for IL2CPP/Mono/UE. It also states the tool's role as session-context setter for all downstream query tools, which cleanly separates it from siblings like find_game_processes or inspect_game.

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

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

Explicitly says all query tools afterwards use this game as context and that switching games resets the session, and it documents the cheap repeat-call path (reused=true, ~10ms). It does not name a competing sibling (e.g., inspect_game vs find_game_processes) or state when not to call it, so it stops short of full routing guidance.

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