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

Annotations already declare this is a non-read-only, non-idempotent write with destructiveHint=true, so the safety profile is covered. The description contributes real behavioral context beyond that: the size ceiling, the exact extension allowlist, and that content must be base64-encoded. It still omits what happens on repeat uploads or whether the call requires case-level authorization.

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?

Three short sentences, front-loaded with purpose and followed by the binding constraints (size, extensions, encoding). Every clause carries actionable information and there is no filler.

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 write tool with annotations present and no output schema, the description covers the invocation constraints an agent needs to avoid failure. It falls short only on what the call returns (e.g., a file ID) and duplicate/replacement semantics, which matters given idempotentHint=false.

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 all six parameters, including the documentType enum with its legacy aliases, are already documented in the schema. The description adds nothing about caseId format, contentType inference, or the enum choices, so the baseline of 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 (attach/upload) and resource (document to a case), and gives concrete examples of the document kinds it handles. It is clearly distinguishable from the sibling list_case_files, which only enumerates 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?

The description supplies hard operational constraints (25 MB cap, allowed extensions, base64 payload), which implicitly tells an agent when this call will succeed. However, it never says when to use upload_case_file versus other case-mutation siblings, nor any prerequisite such as required case state or permissions.

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