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

With no annotations, the description carries the full burden and does disclose key traits: parent directories are auto-created, there is a hard 5 MB inline limit, and a token plus live sandbox_id are required. It does not say whether an existing file is overwritten or what is returned, which leaves a real gap for a write operation.

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?

Dense, imperative and front-loaded: the core action, the alternative-parameter rule, the limit and the fallback path all appear in the first three clauses. The 5 MB cap is stated twice ('Limit 5 MB per file inline' and trailing 'Max 5 MB'), a small redundancy.

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 5-param write tool with no output schema and no annotations, the definition covers prerequisites, size limits, encoding choice and the escalation path. The main omission is the return value / overwrite behavior, which matters for confirming a successful upload.

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 only 20%, so the description must compensate, and it largely does: content vs content_base64 is disambiguated by encoding, path is described as absolute (matching the ^\/ pattern), and mode is exemplified as '755'. Only sandbox_id semantics are left to the schema 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?

States a specific verb and resource ('Write a file into the sandbox at an absolute path') and pins down the scope (inline, 5 MB cap). It also names the sibling get_upload_url as the route for larger files, so an agent can separate it from download_file/get_upload_url 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?

Explicit when-to-use routing: use this for files up to 5 MB, and 'for bigger files call get_upload_url and PUT the bytes to the link'. Prerequisites are stated ('Requires: token + live sandbox_id'), and the 'no base64 through this chat' note excludes a misuse path.

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