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

Annotations are sparse on behavior, but the description adds substantial context the annotations lack: exact price ($0.005), payment asset/chain (USDC on Solana via x402), the required challenge-retry flow, and the _meta key for payment. There is mild tension between the 'GET' read semantics and readOnlyHint=false, but this plausibly reflects the on-chain payment side effect rather than a real contradiction.

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?

Purpose is front-loaded in the first clause, followed by pricing and payment mechanics. The payment and HTTP-equivalent details are dense but each earns its place for correct invocation; only the URL restatement is slightly redundant.

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-param tool with no output schema, the definition covers what an agent needs to know to invoke it correctly, including the non-obvious payment handshake that would otherwise cause failures. Return data shape is unspecified but the source (US Census population) makes it reasonably predictable.

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 100% with a single 'state' filter that is already documented in the schema. The description adds nothing about the parameter (e.g., accepted formats or whether it's an abbreviation vs full name), so the schema carries all meaning — baseline 3.

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 resource (US Census population data) with a concrete retrieval verb implied, and the name plus source give an agent a clear sense of the tool's scope. It does not explicitly differentiate itself from the macro_* siblings (cpi, payrolls, unemployment), leaving that to the names alone.

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?

Provides a detailed payment procedure (challenge-then-retry), which is genuinely useful usage guidance for invocation, but gives no when-to-use rationale or alternatives relative to the other macro_* tools. The usage guidance present is procedural rather than about tool selection.

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