download_by_filename

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

With no annotations, the description carries the full burden and does well: it discloses that return_base64 skips disk writes, that files over 800 KB are auto-converted to WebP to fit base64 limits, and that COMFYUI_HOST is required. It stops short of stating overwrite behavior on dest_path or what happens on a missing filename.

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?

Front-loaded with purpose and the no-prompt_id qualifier, then behavior, then the environment prerequisite. Five sentences, nearly all substantive; 'Uses GET /view' is the only line that leans toward implementation trivia rather than agent-relevant guidance.

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 an 8-parameter tool with no annotations and no output schema, the description supplies the behavioral payload an agent needs: where the filename comes from, the base64-vs-disk branch, size-triggered conversion, and the host requirement. Only the return shape for the non-base64 (file-written) path is left implicit.

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 baseline is 3, but the description adds genuine meaning the schema does not: return_base64 suppresses disk writes entirely, and the 800 KB auto-WebP threshold explains the default for max_base64_bytes. These are interaction semantics rather than restated field labels.

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?

Specific verb+resource: 'Download an output file by filename' with the explicit disambiguator '(no prompt_id needed)' and the underlying endpoint. This cleanly separates it from download_output (prompt_id-based) and download_all_outputs in the sibling list.

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?

'Use when you have filename from get_history or get_last_output' gives a concrete triggering condition and names the upstream tools that produce the input. It does not state the inverse case (use download_output when you have a prompt_id), so the alternative is only implied.

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