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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is established without the description. The description adds genuine context beyond those hints: authentication is a precondition, the billing node is null for Free-plan users, and the response is a nested plan/billing/usage object. No statement contradicts the annotations.

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?

Roughly three sentences pack the primary verb and scope, an itemized breakdown of return contents, a null-case note, an authentication requirement, and the overall return shape. There is no filler, and the main action is front-loaded before the detail clauses.

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 carries the burden of describing the return value and does so thoroughly, including the Free-plan null case and nested structure. Minor omissions – such as explicit error/expired-auth behavior or rate-limit notes – are not critical for a read-only account details fetcher, and the interaction scope is fully visible.

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 50% – feedback is well-documented in the schema, while _requestId is not, and the description adds no per-parameter detail. This is mitigated because both parameters are auxiliary metadata (an optional feedback string and a request tracer) and neither steers the operation; the tool effectively takes zero functional parameters, so the parameter burden is minimal.

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?

Opens with a specific verb-resource pair ('Get authenticated user's account details') and enumerates the exact content areas: plan (name, features), billing (period, renewal; null for Free plan), and usage (subscription credits, extra credits, extra tracked items). This makes it unmistakably distinct from the sibling social-media content tools, which all fetch third-party data rather than the caller's own account.

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 makes the context clear: it is the endpoint for inspecting the authenticated user's own plan/billing/usage state, and it states the authentication precondition. It does not explicitly name alternative tools or spell out when-not-to-use it, but given the sibling set is dominated by content-fetch tools, the scope stated is sufficient to steer an agent.

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