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

With no annotations, the description carries the behavioral burden and does so well: it discloses the temporary return URL, roughly one-hour validity, minimum and maximum file counts, array-order concatenation, pricing, and Lightning payment requirements. It stops short of failure modes, file-size limits, or retry behavior for resultKey, so it is strong but not exhaustive.

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 description is front-loaded with the core operation and then efficiently layers in return behavior, limits, pricing, alternatives, and payment prerequisites. There is no wasted text, and each sentence contributes operational context.

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?

Given the absence of annotations and an output schema, the description supplies the missing return-value, payment, cost, and file-ordering context that an agent needs. It is complete enough for correct selection and invocation, with only minor optional details like error formats omitted.

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%, so the baseline is 3. The description adds useful semantics beyond the schema by explaining that files are concatenated in array order and by tying paymentId to the create_payment flow, though it does not elaborate on resultKey behavior.

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 specific verb and resource: merging multiple PDF files into one document. It also explicitly distinguishes the tool from convert_file, so an agent can identify its exact purpose without inspecting the schema.

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 names the relevant alternative, convert_file, and the condition that selects it: format conversion such as DOCX to PDF. It also states the create_payment prerequisite with toolName='merge_pdfs', giving clear contextual guidance for invocation.

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