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

Annotations already declare destructiveHint=true and idempotentHint=true, so safety is covered. The description adds non-obvious behavior: changes take effect immediately with no deploy, and the workspace is servable at runtime. It does not explicitly say an existing file at the path is overwritten, which would have closed the loop on the destructive hint.

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 the core action in the first sentence, then rationale and use cases. The second sentence is long and carries two ideas (deploy-free shipping, large non-code files), but both earn their place; nothing is redundant with the schema or annotations.

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 4-parameter mutation tool with no output schema and full annotation coverage, the description explains what the tool affects and why it exists. The only omission is explicit overwrite/return behavior, a minor gap given destructiveHint already signals mutation.

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 description coverage is 100%, so path, content, encoding and privateKey are all documented in the schema itself. The description adds no syntax, format, or constraint details 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?

States a specific verb+resource ('Write a file to the lambda's workspace') and immediately characterizes the target as a runtime directory the lambda can read, write and serve. It also distinguishes itself from the code-writing siblings by framing itself as the destination for non-code assets like front ends or large files.

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 context for when to use it ('ship a front end that changes independently of the code', 'large files that are not code'), which implicitly separates it from write_code/change_code. It stops short of naming those alternatives or stating explicit exclusions, so it is clear but not fully routing.

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