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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true. The description adds a key behavioral constraint: 'Simulated resources cannot authorize live effects.' This tells the agent that credentials created here are sandbox-only and cannot be used for live operations. This is valuable context beyond the annotations.

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, zero waste. The first sentence states the action and the second adds the critical behavioral constraint. Both sentences earn their place.

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 single-parameter tool with no output schema, the description is nearly complete. It explains what the tool does, the sandbox limitation, and the parameter is simple enough that the schema covers its type. The only gap is not explaining what the return value looks like (e.g., does it return credentials directly?), but with no output schema and a simple tool, this is a minor gap.

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 0%, so the description must compensate. The description mentions 'credentials' but doesn't explain the 'name' parameter's role (e.g., is it a display name, a unique identifier, a prefix for generated credentials?). The schema only says it's a string with length constraints. The description adds no parameter-specific meaning, so a 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?

The description states a specific verb ('Create') and resource ('free sandbox credentials') and distinguishes it from browser signup. It doesn't explicitly name the sibling 'enroll_live' but the contrast with live enrollment is implied by 'sandbox' and 'without browser signup'.

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 implies when to use this tool: when you need sandbox credentials without browser signup. It doesn't explicitly say 'use enroll_live for live credentials' but the sibling name and the sandbox/live contrast make the usage context clear. No explicit exclusions or alternatives are named.

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