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

Beyond the readOnly/idempotent annotations, the description explains that billable volume counts only LIVE fills, that paper and testnet activity is never billed, and why a paper-only account legitimately reads 0.00 used. It also clarifies the null cap_usd / zero pct_used relationship, which materially changes how an agent should interpret the response.

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?

It is front-loaded with the read scope, followed by the payment exclusion, the billing caveat, and the null-cap rule. The paper-trading explanation is the longest clause, but it earns its place by preventing a common misreading of a 0.00 value.

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?

An output schema exists, so return values need not be enumerated. Given zero parameters and a safe read-only annotation profile, the description covers everything an agent needs: what is read, what is excluded, and how to interpret edge-case values.

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 no parameters, so the baseline is 4 and there is nothing further for the description to disambiguate on the input side. The description spends its space on response semantics instead, which 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 opens with a specific verb and a concrete list of resources: subscription plan, billable volume used, plan cap, and permitted actions. That is enough for an agent to distinguish it from siblings like get_status or get_config, even though no sibling is named explicitly.

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 implied by the resource being read (plan usage and entitlements), and one exclusion is stated: payment details are not included. However, there is no explicit guidance on when to prefer this over get_assurance_status or get_config, so the agent must infer the boundary.

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