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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety is covered; the description adds genuinely new context: the data source (live census vs 2026-10-28 snapshot), the 'never a verdict' framing, and that last-checked/changed timestamps are included. It does not discuss rate limits, authentication, or behavior when an agent id does not exist, which keeps it from a 5.

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?

Content is front-loaded with the resource and scope, and every clause carries real information (largely acting as a return-value summary since there is no output schema). However, it is delivered as one long comma-chained sentence that is dense and harder to parse than a short structured list would be.

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 no output schema, the description carries the full burden of describing return values, and it does so item by item: card load and host, classification, MCP initialize result, x402 payment terms and payTo identity match, wallet activity, and last-checked/change data, plus provenance. For a read-only single-parameter lookup this is complete enough to call and interpret without opening anything else.

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?

There is a single parameter whose schema description is fully covered (token id, range 0–1000000000, example 20030). The prose only restates that the input is the agent id in the identity registry, adding no format or edge-case detail beyond the schema, so the baseline 3 applies.

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 names a specific verb (fetch/check) and a precisely scoped resource: one ERC-8004 agent on Robinhood Chain, identified by agent id, including the identity registry address. It enumerates exactly what is returned (card load, class, MCP initialize, x402 402 response, payTo vs agentWallet, wallet activity, last-checked/changes), which cleanly separates it from siblings like check_coin, check_tx and larp_check.

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?

Usage context is clear: it is scoped to Robinhood Chain only, framed as plain census facts rather than a verdict, and it discloses that data may come from the live census or a dated snapshot. It never explicitly names an alternative sibling or states when-not to use it, so it stops short of full routing guidance.

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