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

No annotations are provided, so the description carries the full burden. 'Show' implies a read-only operation and 'works for guests too' is a useful auth/permission disclosure. Beyond that, it says nothing about rate limits, caching, or whether the returned plan data can be stale — modest coverage for what is a low-risk, zero-parameter read.

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 short sentences, both front-loaded with the most decision-relevant information (what is shown, then who can call it). No filler and nothing redundant with structured fields.

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 and no annotations, the description is the sole source of information, and it identifies the data returned (plan, usage vs. limits, upgrade/key paths) plus the guest-access condition. That is sufficient for an agent to call a zero-parameter read correctly, though it could note whether the response differs for guests.

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. There is no parameter semantics to document and the description correctly avoids inventing any.

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 ('Show') and enumerates the resource content: current plan, usage against limits, and upgrade/key locations. The resource ('account') is clear enough that no sibling differentiation is needed, since the sibling tools are all page-related operations.

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 line 'Works for guests too' implies the calling context (no authenticated account required), which is genuine usage guidance. However, there is no explicit when-to-use or when-not-to-use framing, and no named alternative for users who want account-mutating operations.

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