get_billing

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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds genuinely useful context by disclosing the required auth scope (billing:read), but says nothing about the size or window of "recent ledger lines", whether results are paginated, or the response shape.

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?

Two compact clauses, with the returned data front-loaded and the auth scope trailing. The fragmentary "Scope billing:read." is telegraphic but not wasteful.

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 parameters and no output schema, the description is the only source of truth about what comes back, and it lists the three result categories. However, it omits how far back "recent" extends and whether there are limits on ledger lines, which an agent needs to interpret the result.

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 there are no parameter semantics to explain; the baseline of 4 applies. The description correctly implies no inputs are needed to scope the query.

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 names the concrete resources returned: account balance, monthly spend, and recent ledger lines, which lets an agent distinguish this from the server/DNS/database siblings. It lacks an explicit verb phrase like "Retrieve" but the resource set is unambiguous.

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?

Usage is only implied: an agent needing billing data would select this, but nothing states when to prefer it, when not to use it, or whether it overlaps with get_order. No alternatives are named or ruled out.

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