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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint; the description adds genuinely new context by specifying it requires OAuth and derives identity from the bearer token. That auth requirement is not encoded in the annotations, so it earns credit, though nothing is said about failure modes (e.g., missing/expired token).

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?

Three tight sentences with zero filler, and the payload is front-loaded. The final sentence ('read-only helper... for calls from the app UI') partially restates what readOnlyHint already conveys, a minor 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 output schema present and full annotation coverage, the description only needs to supply identity/auth and intent context, which it does. Nothing an agent needs to call this zero-param tool correctly 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?

The tool takes zero parameters, so the baseline is 4; there is no parameter syntax the description could or should document.

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 ('Returns the authenticated user's id, full_name, email and created_at') and enumerates the returned fields. It is clearly distinguishable from the sibling write tools (create_bill, update_bill, set_bill_selections_batch), which all mutate bill data.

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 clear context — it exists so the bill UI can identify the user's own selections — which is a usable 'when to use' signal. It does not name an alternative or an explicit 'when not to use' condition, so it falls short of a 5.

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