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

With no annotations provided, the description carries the full behavioral burden. It clearly states the returned data categories and discloses an important behavioral constraint: the tool should not be used as a preflight because account scope and tier enforcement are handled elsewhere. This goes beyond a bare 'whoami' description, though it stops short of describing the exact response format.

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 three tight sentences with no filler. The primary purpose is front-loaded first, usage conditions follow, and the critical exclusion is clearly flagged with 'NOT a preflight'. Every clause earns its place.

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 zero-parameter, no-output-schema tool, the description is fully sufficient. It tells the agent what the tool returns, when to call it, and when not to call it. No additional context is needed for correct selection and invocation.

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?

The tool takes zero parameters, so the baseline of 4 applies. The description adds no parameter-level detail because there is nothing to document; the input schema is already complete at 100% coverage.

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 uses a specific verb ('Returns') and names the exact resource: the calling user's identity, tier, surface, and selected connected account. It also distinguishes this tool from preflight-style checks by explicitly saying it is NOT a preflight, which disambiguates it from the many sibling tools.

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 states precise conditions for use ('when the user asks who they are, what plan they are on, or which account is selected') and gives an explicit exclusion ('NOT a preflight — never call it to check the account or tier before a write'). It also explains why the exclusion exists, referencing available context and server enforcement.

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