Download an ECFS document

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

With no annotations, the description carries the full burden and does real work: it discloses the headless Chrome dependency, the latency cost, the forced .pdf extension, and the fixed download location (ECFS_DOWNLOAD_DIR, default ~/Downloads/ecfs). It leaves out auth needs, overwrite behavior on repeated downloads, and failure modes, which keeps it below a 5.

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 action and outcome are front-loaded in the first sentence, followed by identification semantics, then operational caveats. Four sentences, each carrying distinct information with no filler.

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 side-effecting download with no output schema, the description covers prerequisites, timing, destination, and return value adequately. It stops short of describing error behavior or what happens on filename collisions, which an agent invoking a disk-writing tool would benefit from.

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 all three parameters are already documented in structured form, including the same {n} URL mapping for document_number and the subfolder rules for output_dir. The description restates the URL-position concept rather than adding syntax or edge-case meaning beyond the schema, so the baseline 3 applies.

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 opens with a specific verb and resource — 'Download one document (usually a PDF) from an ECFS filing and save it to disk' — and states the return value (saved file path). It is clearly a retrieval/save tool, distinguishable from siblings like ecfs_search_documents or ecfs_get_filing without opening any 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 explains how to select the right document (submission ID plus the {n} position in the document URL) and adds operational context — a headless Chrome requirement and a few seconds per document. It does not name alternatives or explicitly say when to prefer ecfs_get_download_plan or ecfs_search_documents instead, so it falls short of full routing guidance.

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