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

Annotations only supply readOnlyHint=false, so the description carries most of the burden: it declares no money moves, names the endpoint, and specifies the three return values (goalId, paymentUrl, clientSecret), including the hosted-vs-embedded distinction. It does not state auth/rate-limit behavior or webhook side effects, but the value-add over annotations is substantial.

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 with zero filler; the operation, the safety guarantee, and the return shape are front-loaded in that order.

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 11 params, nested metadata, and no output schema, the description usefully explains return values and the no-charge guarantee. Minor gaps remain around error behavior and what happens with callbackUrl/cancelUrl redirects, but nothing essential to correct invocation 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?

Schema coverage is 73%, so the schema already documents most parameters in detail (deadline window, depositAmount rules, frequency semantics). The description adds only a global unit/currency clarification ('integer cents, USD'), which largely restates targetAmount's own schema description. 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 ('Creates a goal') plus the underlying endpoint and mode ('test key'), and immediately rules out side effects ('No money moves'). This cleanly separates it from cancel_test_goal and the other test-mode siblings without ambiguity.

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 test-key framing implies this is the sandbox path, but the description never states when to choose it over a live counterpart or what must happen first. The prerequisite (register_test_provider) only surfaces in the schema's providerLinkCode description, so guidance here is implied rather than stated.

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