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

Annotations only assert readOnlyHint=true, but the description adds substantial behavior beyond that: the meaning of each terminal state, polling cadence, the auth prerequisite (needs a Proof account; authenticate via /mcp or start_login), and the non-obvious requirement that the user-facing reply text must already surface the challenge link/SMS before this call.

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 core purpose and return states are front-loaded in the first sentence, and the polling/terminal-state guidance follows logically. Slightly long across three paragraphs with some overlap between the return-state list and the terminal-state explanation, but every section carries actionable information.

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 compensates by enumerating the possible status values and their meanings. Auth requirements and the pre-call reply-text obligation are also covered, so an agent has everything needed to call and interpret this correctly.

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 single session_id parameter is fully documented in the schema, so the schema already carries the semantics. The description says 'by session ID' but adds no format, provenance, or sourcing detail beyond it, making the baseline 3 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?

States a specific verb and resource ('Check the status of a 2FA session by session ID') and enumerates the return states (completed/pending/expired), which lets an agent separate it from siblings like verify_2fa, wait_for_2fa, and start_2fa 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 strong operational context: poll after start_2fa, cadence of 'every few seconds', and explicit terminal-state handling ('verified' proceed, 'expired' restart with start_2fa). It does not, however, mention the sibling wait_for_2fa, which is the obvious alternative to hand-rolled polling, so the alternative-space is not fully closed.

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