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

With no annotations, the description carries the behavioral burden. It discloses the authentication requirement, the conditional return of a proof token, and that start_login has no side effect on this tool. It doesn't mention error behavior or non-verified sessions, but for a simple read it's reasonably transparent.

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 description is concise and front-loaded: the purpose and return content are in the first sentence, and the access note is separated clearly. Every sentence contributes value, with no 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?

For a single-parameter get tool with no output schema, the description covers the essential context: what it returns, that auth is needed, and a specific workflow. It doesn't cover error handling or session ID format, but those are either covered by schema or minor for this type of tool.

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 100% and the description adds no new meaning to the 'id' parameter beyond what the schema already states ('Session ID'). The mention 'by ID' simply restates the schema, so a baseline 3 is appropriate.

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 states a clear verb ('Get'), a specific resource ('a session by ID'), and the return content ('session status, verification details, and proof token if verified'). This distinguishes it from siblings like create_session or wait_for_session, which are about creation or polling.

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 provides explicit access prerequisites (a Proof account and authentication) and clarifies that start_login does NOT open this tool, which is a useful negative instruction. It doesn't explicitly name alternative tools for retrieving session info, but the workflow context is clear enough.

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