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

With no annotations, the description carries the burden well: it discloses the paid model ($0.005 USDC per call via x402, payment passed in _meta["x402/payment"]) and a free 3-row preview mode, which are non-obvious operational facts an agent must know before calling. It does not cover pagination behavior, error/payment-failure handling, or result shape.

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?

Three compact sentences: identity first, then routes, then cost/free-preview escape hatch. No filler, and the actionable cost information is where a caller will look for it.

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 3-parameter dataset lookup with no output schema, the description covers resource scope, route selection, searchable fields, cost, and a free preview path — enough to invoke correctly without further reading.

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%, but the schema only lists route values generically; the description enumerates the actual search query keys (q, country, status, category, limit, offset), which meaningfully exceeds the schema. The 'sample' and _meta payment semantics are also clarified beyond the schema's one-line hints.

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 ('Stock Exchanges and Trading Venues (MIC)') and a clear lookup action, with target audiences (fintech apps, trading bots, data pipelines) that set the domain. It is unambiguous against siblings like airports or markets, though it never explicitly says how it differs from markets/regions.

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?

Names both routes and their use conditions ('/{mic}' for a specific venue vs '/search' with q/country/status/category/limit/offset), and gives a concrete fallback for cost-sensitive calls ('set sample=true for a free 3-row preview'). No explicit when-not-to-use guidance or pointer to a sibling for related data.

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