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 meaningful work: 'never pays' rules out the destructive/transactional risk an 'x402' tool would otherwise imply, and it discloses the cost model (free in the MCP playzone, $0.002 via x402 in production). It does not cover error behavior for an unreachable or malformed URL, rate limits, or whether results are cached, so it stops short of full disclosure.

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 primary purpose and the contents of the card are front-loaded in the opening sentence, and the scope constraint follows immediately. Some material does not earn its place for an agent, notably the 'By OMENZ.' branding and the production REST URL, though the 'free playzone' note usefully reinforces the no-payment behavior.

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 tool with no output schema and no annotations, the description compensates well on the return side by enumerating the card's fields. The main remaining gap is the undocumented `method` parameter. Error handling and pagination are not addressed but are less critical for a read-only card fetch.

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 0%, so the description must explain both parameters. The phrase 'a service index or a single endpoint' partially clarifies what values `url` accepts, but the `method` parameter is never mentioned anywhere and its meaning is left entirely to inference. That leaves the second of two parameters undocumented.

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?

Names a concrete artifact and enumerates its contents (endpoints, live prices, payment options, input/output examples, latency), so the agent knows exactly what it gets back. It states the accepted inputs (a service index or a single endpoint) and the 'never pays' constraint. It does not name or contrast any sibling, so an agent must still guess its relationship to tools like market_price_index or cost_estimate.

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?

'Works on a service index or a single endpoint' gives a usable scope statement, and 'never pays' tells the agent this is a safe inspection call. There is no explicit when-to-use versus when-not, and no guidance on choosing this over other pricing/discovery siblings, so the guidance is implied rather than stated.

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