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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing per-call cost ($0.001 USDC via x402), the exact failure mode (returns payment requirements instead of results), and the two retry mechanisms. Also discloses that input is never mutated or truncated, which matters for a normalization tool. This is exactly the kind of protocol and cost context annotations cannot carry.

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?

Four short sentences, front-loaded with what the tool does before constraints and payment mechanics. Dense rather than padded; the only slightly crowded element is the compressed payment-retry clause, which packs three header options into one sentence.

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?

With readOnly annotations, no output schema, and full schema coverage, the remaining burden is cost, failure behavior and semantics of results, and the description covers cost and payment failure. The one gap is what the tool returns: it mentions a 'warning length' limit but never explains what warning is emitted or whether normalized titles come back as an array.

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 titles, maxLength and its bounds are already documented, making 3 the baseline. The description reinforces non-truncation but adds no new meaning about maxItems, batching limits, or what a 'warning' actually returns. It also references params._meta['x402/payment'] as an accepted input shape that does not appear in the schema (additionalProperties: false), which an agent may find ambiguous.

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 verb and resource ('Normalize caller-supplied product titles') and names the exact technique (Unicode NFKC plus whitespace cleanup), so the agent knows precisely what transformation happens. No sibling is named as an alternative, but none of the listed siblings overlaps closely, so differentiation is implicit rather than explicit.

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?

Boundary conditions are stated in the negative form that matters here: 'No translation or truncation' and 'originals preserved' tell the agent when this tool is and isn't the right choice. It also gives concrete invocation guidance for the payment failure path (retry with X-PAYMENT, PAYMENT-SIGNATURE, or params._meta['x402/payment']). It stops short of naming a preferred alternative when translation is actually needed.

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