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

Annotations mark this as a mutation (readOnlyHint=false, destructiveHint=true) and the description does not contradict that. It adds real behavioral context annotations can't convey: the return contract (saved: true, download_url) and the instruction to link it as [filename](download_url). It does not say what happens if a file of the same name already exists, which matters for a destructiveHint tool.

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-loads the core action and the most likely case (CSV) in the first sentence, then layers extensions, the failure caveat, and the success contract. Every sentence carries distinct information; nothing repeats the schema.

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 two-parameter tool with no output schema, the description covers the return payload (saved flag, download_url) and how to present it, which is exactly the gap structured fields leave. The only omission is overwrite/collision behavior, which is worth a sentence given destructiveHint=true.

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 still adds value beyond the schema by constraining the accepted extensions and sketching the CSV layout (header row then one row per line), which tells the agent how to shape content before calling.

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?

States a specific verb and resource (save text as a downloadable file in the Second Brain) plus the concrete artifact types it produces (CSV, TSV, TXT, MD, JSON), which distinguishes it from generate_pdf, generate_markdown and save_file_from_url. An agent can tell what it produces without opening 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?

Gives clear positive conditions (a contact list, export, table for a spreadsheet) and a strong negative one: files written to a sandbox or temp folder disappear, so this is the only way to hand a file over. No sibling tool is named as an alternative, which keeps it short of a 5.

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