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

Beyond the annotations (readOnly/idempotent/openWorld), the description discloses meaningful behavior: one vector pass, ~200ms, no LLM call, hybrid keyword-fill, and a ranked output with price plus a 'works well with' hint. These are decision-relevant traits — cost, latency, and mechanism — that the annotations cannot express.

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?

Front-loaded with the essential 'discovery, not execution' distinction and reasonably tight, but phrases like 'hybrid keyword-fill so nothing is missed' and the trailing example lean promotional and could be trimmed without losing information.

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?

An output schema exists, so return values need not be explained, and the description still covers scope (16k+ entries, two catalogs), latency, cost profile, and call timing. Nothing an agent needs to invoke it correctly is missing.

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 k, registries, and max_price_usdc are already documented in the schema. The description only restates that input is 'an agent task in plain words', adding no syntax, format, or defaulting detail beyond the schema, which is the baseline-3 case.

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 precise verb+resource — 'Tool/service DISCOVERY, not execution' over a merged x402 Bazaar + MCP Registry catalog — and explicitly contrasts the tool with execution tools. An agent can immediately tell this is a routing/search step, not a task performer.

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 an explicit call condition: 'Call this FIRST, before loading candidate tools into context, whenever you do not already know which tool serves a task.' The negative case (when you already know the tool) is implied by that phrasing, and the supplied example task makes the intended invocation concrete.

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