Start a playtest (you play)

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

Annotations declare it is a non-read-only, non-open-world, non-idempotent operation, but add nothing about constraints. The description supplies the real operational facts: an implicit build step (unless build:false), a returned session id plus first screenshot, a 40-action cap per session, 2 concurrent sessions, idle auto-close after a few minutes, and no login required.

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?

The key fact (starts the game for manual play) is front-loaded and every sentence carries information: purpose, workflow, limits, environment. It is densely packed with parentheticals and semicolon chains, which costs a little readability but no sentence is wasted.

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?

For a session-starting tool with no output schema, the description covers what an agent needs: what is returned, which siblings continue the workflow, hard limits, session lifetime, and that no auth is involved. Nothing required to invoke it correctly is missing.

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 100%, so the schema already explains dir, build, and the desktop/mobile profile enum; baseline is 3. The description adds only one detail beyond the schema — that the build runs first unless build:false — and says nothing about profile differences (viewport/touch behavior) that would help an agent choose.

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?

States a specific verb and resource ("Starts the game ... in headless Chromium inside the autotest harness so you can play it yourself") and explicitly distinguishes it from the sibling gamealia_run_autotest by naming the case it can't cover ("gameplay the automatic gamealia_run_autotest cannot judge"). An agent can tell it apart from gamealia_preview and gamealia_run_autotest without opening any schema.

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?

Gives the when-to-use condition (manual gameplay judgment the autotest can't make) and the full lifecycle: call gamealia_playtest_act one action at a time, then gamealia_playtest_stop for the verdict. It also names the action vocabulary (click x,y | key | drag | wait), removing ambiguity about what happens next.

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