s3_download_object

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

With no annotations provided, the description carries the full burden of disclosing behavioral traits. It explicitly states a key safety behavior: local_path must resolve under allowed roots, and paths outside are rejected. This goes beyond the schema's simple parameter description. However, it does not cover other important behaviors like overwrite policy, error handling, or file creation behavior.

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 two sentences: the first clearly states the purpose, the second adds a critical safety constraint. No superfluous words. Front-loaded with the core action. Appropriate length for the tool's simplicity.

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 no output schema and no annotations, the description covers the purpose and a key safety constraint, but lacks details about what happens on success (file saved), overwrite behavior, or error scenarios beyond path rejection. For a download tool, completeness is moderate but could mention post-download state or permissions.

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?

The schema covers all 4 parameters with descriptions (100% coverage), so baseline is 3. The description adds significant value by clarifying that local_path must resolve under specific directories (home, cwd, ~/Downloads), which is a critical constraint not present in the schema's generic 'Local file path' description.

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+resource: 'Download an object from S3 to a local file.' It clearly distinguishes from sibling S3 tools like s3_copy_object, s3_upload_object, etc., which have different actions.

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 provides no guidance on when to use this tool versus alternatives. It does not mention any exclusion criteria or suggest other tools for related tasks (e.g., copying, uploading). The only contextual hint is the path safety restriction, which is a constraint, not a usage guideline.

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