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 covered. The description adds real value beyond that by disclosing the OAuth-vs-api_key authorization path and the consequence of omitting the key, which an agent cannot infer from the annotations alone.

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 sentences: the first front-loads what is returned (balances, spending allowance), the second handles the auth precondition. Efficient, though the second sentence partially duplicates the api_key schema description, adding mild redundancy.

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 zero-required-parameter read tool with no output schema, the description adequately conveys what comes back (stablecoin balances plus remaining allowance) and how to authenticate. Nothing essential to invoking it correctly is missing, though return shape specifics are absent.

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%, so both parameters are fully documented in the schema, including the chain default and the 'omit when OAuth' note. The description largely restates the api_key guidance already present in the schema, adding no new syntax or format detail — baseline 3 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?

States a specific verb and resource: 'Check a linked wallet's stablecoin balances and remaining agent spending allowance.' An agent can tell this apart from pay_bill or schedule_bill, but it never distinguishes itself from transaction_history, the closest sibling, leaving a small ambiguity about balance-snapshot vs. history retrieval.

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 explains the two auth modes (OAuth connector vs. passing an api_key) and that no arguments are needed when authorized, which is genuine call-time guidance. However, it offers no when-to-use/when-not guidance relative to siblings like transaction_history, so usage selection is only implied.

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