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

Annotations already declare readOnly/idempotent/non-destructive/non-open-world, so the safety profile is covered. The description adds real behavior beyond that: Creator Pack credits never expire but are consumed ('do not come back'), free-account exports may draw down that pack, and plan limits are authoritative across web and MCP. It does not describe response shape, though no output schema exists, so a point is withheld.

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?

Front-loaded with the core purpose, then usage guidance. The parenthetical enumerating every limit is dense but each item is decision-relevant (footer credit and AI allowance affect what the agent can do). Slightly long single sentence early, but nothing is wasted.

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 return-value burden, and it does so by naming each reported field group. For a zero-parameter read tool, an agent has everything needed to call it and 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 is no parameter meaning to convey and the schema is trivially complete. The description does not need to compensate for anything here; baseline 4 applies.

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?

Specific verb+resource: reports the plan the API key belongs to, the limits that apply, and the Creator Pack balance. The enumerated limit list (content pages per PDF, saved projects, Brand Themes, footer credit, AI allowance) makes it unambiguous and clearly distinct from every sibling tool, none of which read account state.

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?

Explicit when-to-call: 'Call this BEFORE writing a long ebook so the draft fits the user's plan, and before exporting on a free account, where a long export uses a Creator Pack export.' It also closes off the wrong assumption by noting that MCP does not change the limits seen in the web app.

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