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

Annotations already provide readOnlyHint=true, so the read-only nature is covered. The description adds context about 'public-safe' state and the session-scoped access, which goes beyond the annotation by clarifying what subset of data is returned and the security model. No contradiction.

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?

Two sentences, no fluff, the core action is front-loaded. The scope constraint is stated immediately after the verb. Perfectly concise.

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?

Given it's a simple read tool with two required parameters and no output schema, the description covers the key context: what is read, the security scoping, and the read-only nature (via annotations). It does not describe return format or error behavior, but for a read-only state fetch this is acceptable.

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 coverage is 0% – neither parameter has a description in the schema. The description mentions the sessionToken grants access only to that session, which gives meaning to the token, but it never explains sessionId. With low coverage, the description should compensate for both parameters; it only partially covers one.

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?

The description clearly states the verb 'Read' and the resource 'public-safe state of a game session', which is specific and distinguishes it from siblings like arcade_make_move (write) and arcade_start_game (mutates). The scope is explicitly tied to the session token.

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?

The description implies use for reading without side effects ('public-safe', 'Read'), and the sibling set makes the distinction clear. However, it does not explicitly name alternatives or state when not to use it, only that the token grants access to that session.

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