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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It explicitly states that the first call does not charge anything, that the second call verifies and settles payment, and that a failed or already-used signature raises an error rather than silently no-op'ing. It also notes that the tool cannot sign for the user, which is critical behavioral context. This fully compensates for the lack of 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?

The description is well-structured with clear step-by-step instructions separated by newlines. It front-loads the key information about the two-step nature and the constraint on trial workspaces. Every sentence adds value, covering prerequisites, the two steps, the return value, and error behavior. It is appropriately sized for the complexity without being verbose.

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?

Given the tool's complexity (two-step x402 protocol), the description is complete. It covers the full flow, prerequisites (owner_key), error handling, and the return structure (workspace_id, deposited_units, tx_hash, network). There is no output schema, so describing the return format is essential and is provided. The description leaves no gaps that an agent needs to invoke the tool correctly.

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?

The input schema has 100% coverage of all 4 parameters, each with detailed descriptions (e.g., api_key explains it can be owner_key or sub-key, amount_usd explains decimal string and minimum, payment_signature explains the two-step usage). Since the schema already provides comprehensive semantics, the description adds marginal value by reinforcing the two-step flow, but does not need to compensate for any gaps. Baseline 3 is appropriate as 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 clearly states the tool's purpose: to fund a real workspace via the x402 protocol. It specifies the action (fund), the resource (workspace), and the method (x402 protocol). It also distinguishes itself from the sibling aanet_create_workspace, noting that trial workspaces are not accepted, which helps differentiate it in the context of sibling tools like aanet_create_trial_workspace.

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 provides explicit when-to-use guidance: it tells the user to call the tool in two steps, explains the exact sequence (first call without payment_signature to get a challenge, then second call with the signed proof), and states that trial workspaces should not be used (use aanet_create_workspace instead). It also indicates that the tool requires the owner_key, and that the tool cannot sign the challenge itself, so sign with an external client. This is comprehensive and leaves no ambiguity about usage.

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