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

Beyond the readOnlyHint/idempotentHint annotations, the description discloses the exact behavior for both session states: anonymous returns authenticated:false with a hint (not an error), signed-in returns the GitHub-rooted id, login, and tariff. It also discloses the OAuth prerequisite, which is not present in the annotations or schema.

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?

Every sentence earns its place: purpose, behavior, then usage guidance. The key scoping information ('Report the current session's identity') is front-loaded, and the rest is concise without redundancy.

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 an empty input schema, readOnly/idempotent annotations, and an output schema already present, the description supplies the remaining context: failure semantics, exact return shape, and when to call it. Nothing needed for correct invocation 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?

There are zero parameters, so the schema carries no parameter semantics to interpret. The description fully compensates by explaining what the call returns, which is all an agent needs to call and interpret the tool.

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 opening sentence 'Report the current session's identity' names a specific verb and resource, and the subsequent lines specify exactly what is returned for anonymous vs signed-in sessions. This clearly distinguishes it from the sibling tools register_identity and store_memory, which concern writing identity/memory rather than reading the current session.

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 gives explicit context: call it to confirm identity before register_identity/store_memory, and it notes that an anonymous caller must sign in via GitHub OAuth first. It does not explicitly say when not to use it or name alternatives, so it misses the 'when-not' criterion for a 5.

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