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

Annotations indicate non-readOnly, non-destructive behavior, which the description affirms ('source renders are left untouched'). The description goes beyond annotations by detailing billing implications ('Billed as one additional render'), authentication requirements ('Kamy API key with `render` scope'), and failure behavior (atomic failure on any bad id). No contradictions with annotations.

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?

Every sentence earns its place: operation, ordering, preconditions, limitations, side effects, billing, auth. The description is front-loaded with the core action, two sentences long, and no filler. Highly efficient.

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 tool's moderate complexity (2 params, no output schema), the description is fully sufficient. It covers input constraints, failure modes, billing, auth, and relationship to siblings. No gaps remain for an agent to make an incorrect invocation.

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 value by reinforcing the ordering constraint ('in exactly the order the ids are given') and the atomic failure condition, which the schema's JSON description implies but doesn't state as clearly. The `name` parameter is well-contextualized as a label in the description's example ('Q3 statement bundle'). A 4 is warranted because the description meaningfully enriches the schema's semantics.

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 uses a specific verb ('Concatenate') and resource ('existing renders into a single new PDF'), clearly states the input range (2–20), and distinguishes this tool from siblings like 'split_pdf' and 'edit_pdf'. The context of being a composition step after other render calls is 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?

The description specifies exactly when to use this tool ('composition step after several render_pdf / convert_document / edit_pdf calls'), what it cannot do ('cannot merge arbitrary URLs or raw bytes'), and clear failure conditions ('every id must belong to this account and point at a completed render or the whole call fails'). This contrasts well with sibling tools that might handle raw input or single-document operations.

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