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

Annotations already declare readOnly/idempotent/no-destruction, and the description adds genuinely new context: the response is EUR cents (integer) plus a formatted EUR string, and it discloses the auth requirement and that a missing API key produces an auth instruction rather than an error. That return-shape and auth-failure behavior are valuable since no 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?

Three tight sentences: purpose, usage timing, and return/auth behavior, in that order. Every sentence carries distinct information with no repetition of the title or annotations.

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 parameterless read tool with no output schema, the description fully covers what an agent needs: what it returns, when to call it, and what happens when unauthenticated. Nothing material is missing.

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?

Zero parameters, so the baseline is 4; there is nothing for the description to disambiguate. It correctly says nothing about inputs, avoiding noise.

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 ('Returns the current Strale wallet balance') and is unambiguous against siblings like strale_execute or strale_transaction, which do not read balance. An agent knows exactly what this tool yields without opening any schema.

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?

Gives explicit when-to-use triggers ('before executing paid capabilities to verify sufficient funds', 'after a series of calls to reconcile spend'), which implicitly points at strale_execute. It stops short of naming an alternative or stating a when-not-to-use condition, but no sibling overlaps here.

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