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

Annotations already declare a safe, non-destructive, idempotent read profile, so the bar is lower. The description adds real behavioral context beyond annotations by explaining the economic semantics of the returned fields — that spendable equals apiPackCredits plus packCredits, and that weeklyCredits is cosmetic and unusable for MCP/HTTP generation. This prevents an agent from misinterpreting the wallet data. Not a 5 because it does not address the output schema details, though an output schema exists.

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?

Four sentences, no filler. The core action is front-loaded, each subsequent sentence clarifies wallet semantics or usage routing, and the final sentence ties the purpose to a sibling. A minimal, efficient definition that earns every word.

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?

For a low-complexity getter with a 100%-documented parameter, an output schema, and safety-carrying annotations, this description covers what matters: when to call it and how to interpret spendable vs display-only credits. Minor gap: it doesn't enumerate which siblings are the 'paid tools,' but that's inferable from the sibling list and the explicit buy_credits reference.

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 description coverage is 100%: include_notes is fully documented in the input schema. The description reiterates the weeklyCredits non-spendable note that the parameter would include, but adds no new parameter-level meaning beyond what the schema already provides. Baseline 3 is appropriate when the schema does the heavy lifting.

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 resource ('Return the API wallet') and then defines the wallet's structure, distinguishing spendable credits from display-only weeklyCredits. It clearly differentiates from sibling manga.buy_credits by framing this as the check-before-buy operation, so an agent can't confuse the two.

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 guidance is given: 'Use this before a paid tool to see if you need manga.buy_credits.' This states when to call, flags the alternative tool, and even explains the decision criterion (weeklyCredits does not pay MCP or HTTP generate, so it should not count toward affordability). No inference is required.

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