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

With no annotations, the description carries the full burden of behavioral disclosure. It transparently reveals that the call is paid and specifies the cost, which is critical for an agent's decision-making. It also discloses that the endpoint returns the observed block number, giving insight into the response. It does not explicitly claim read-only, but the nature of a balance query implies it. It lacks mention of rate limits or error behaviors, but for a simple read operation, the disclosure is adequate.

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 extremely concise, consisting of exactly two sentences. The first sentence states the core function, and the second adds critical cost and response details. There is no extraneous text, redundancy, or padding. Every word earns its place, making it a model of efficient writing.

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 simplicity (single parameter, no output schema), the description covers the essential context: purpose, cost, and a hint about the response (observed block number). It does not explicitly describe the balance amount format, but the absence of an output schema means the description should at least mention what is returned, which it does. The cost disclosure is a notable addition that makes the tool's usage expectations clearer. A small gap is that the relationship between the balance and block number is not fully elaborated, but overall it is sufficient for a straightforward balance checker.

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% description coverage with a pattern and a clear description for the only parameter 'address'. The description does not add additional parameter semantics beyond what the schema provides; it reiterates that the address is on Base. The baseline of 3 applies because the schema already documents the parameter fully, and the description does not enrich it further.

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 function: 'Return the current USDC balance for an EVM address on Base.' This is a specific verb (return) + resource (USDC balance) + scope (Base network), and it differentiates from siblings like signal_sprint_base_block and signal_sprint_base_gas_price which target different data types on the same network.

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 practical usage context by noting the paid nature of the endpoint ($0.005 via x402) and the REST endpoint path, which helps an agent decide whether to incur cost. However, it does not explicitly state when to prefer this tool over alternatives or list exclusions. The sibling tools cover other Base data, so the purpose alone largely implies when to use it, but explicit guidance is missing.

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