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

With no annotations, the description carries the full behavioral burden and does a good job: it reveals the underlying registry, that it is updated hourly by APEX Watchtower, the exact return fields, the free tier with 200 calls/day, and what this tool is not (the full directory). It stops short of describing query matching behavior or result limits, but the disclosed information 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?

Two sentences contain the core action, search scope, return fields, rate limit, and a pointer to the sibling tool. Every clause earns its place, and the most important purpose information is front-loaded.

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 simple two-parameter search tool with no output schema, the description covers the essential fields returned and the data source. It also gives a helpful alternative for richer data. It could mention result ordering, pagination, or no-result behavior, but these are minor gaps given the tool's simplicity.

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 100%, so the schema already fully documents query and payableOnly. The description adds context by mentioning search is by name/endpoint and that results include whether the agent can be paid on Arc, which aligns with the payableOnly parameter. However, it does not materially extend the parameter meaning beyond the schema.

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 states a specific verb and resource: 'Find an agent on Arc by what it is called or where it answers', then defines the search scope as Arc's ERC-8004 registry. It also differentiates itself from the sibling arc_agent_market by clarifying that this tool returns a subset of fields rather than the full directory with owners and every service.

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 makes the use case clear: searching across agents by name or endpoint. It points users to arc_agent_market when they need the full directory, owners, and every service. It does not give explicit exclusions for other related siblings like arc_agent_status or arc_agent_reputation, but the primary alternative is clearly named.

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