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

With no annotations supplied, the description carries the full burden and does so well: it names the data source (ERC-8004 registry via APEX Watchtower), the refresh cadence (checked each hour), the exact return payload (id, status, uptime over measured hours, payable-on-Arc flag, main endpoint), and the rate limit (200 calls/day). That is behavioral context an agent cannot get from structured fields here.

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 core verb and scoping phrase are front-loaded, and a single colon-led list packs source, output fields, price, and the alternative sibling without filler. It is dense rather than wasteful, though the single run-on sentence makes the alternative-tool hint slightly easy to miss.

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 two-parameter, no-annotation, no-output-schema tool, the definition covers provenance, freshness, cost, and expected return fields, so an agent can decide and call correctly. It omits result-count or pagination behavior and what happens on zero matches, which are the remaining operational unknowns.

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%, so both query and payableOnly are already documented in the schema, which sets the baseline at 3. The phrase 'by what it is called or where it answers' and the mention of 'whether it can be paid on Arc' loosely mirror the two parameters but add no syntax, matching behavior, or edge-case detail 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 opens with a specific verb and resource: find an agent on Arc by name or endpoint. It scopes the corpus to agents the APEX Watchtower checks hourly in the ERC-8004 registry, and explicitly contrasts itself with arc_agent_market as the full directory. An agent can distinguish it from the closest sibling without opening either schema.

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?

It gives a concrete routing rule: use this for lookup by name/endpoint, and use arc_agent_market when you need owners and every service. It also states cost and quota (free, 200 calls a day), which shapes invocation frequency. It does not address other plausible alternatives such as arc_agent_status or arc_agent_reputation, so it stops short of a fully explicit when-not matrix.

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