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

With no annotations, the description carries the full burden, and it does disclose meaningful behavior: per-result pricing, an X-PAYMENT header requirement, a 100-result free trial, and the fact that output includes a signed omission receipt (implying truncation). It still omits what gets omitted or discarded, whether shaping is reversible, and any auth requirements beyond payment.

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?

Two sentences, front-loaded with the action and outputs before the pricing clause, with no obvious filler. It is compact for the amount of information conveyed, though the arrow notation is terse to the point of ambiguity.

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 tool with six undocumented parameters, nested objects, no annotations, and no output schema, the description is far too thin. An agent cannot determine what to put in args, result, tool_args, or fixture_tool from this definition alone.

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% across six parameters, including nested objects (args, result, tool_args), so the description must compensate and largely does not. 'Per-route budgets' weakly hints at the required 'route' parameter, but args, text, result, tool_args, and fixture_tool are entirely unexplained in both schema and description.

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 verb ('Shape') and resource ('one tool result') and names the outputs ('shaped window + signed omission receipt'), so the general action is inferable. However, 'shape' is opaque jargon that is never defined, and the description never distinguishes this from the sibling tools fetch_slice and verify_receipt, leaving the agent to guess the division of labor.

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?

There is no guidance on when to call this versus fetch_slice or verify_receipt, nor on prerequisites (e.g., that a route must be configured with budgets). The only context given is pricing and trial terms, which describe cost, not usage conditions.

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