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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent write. Beyond that, the description adds genuinely useful behavior: a 10MB decoded size ceiling, where the attachment surfaces afterward (web task view, list_task_files), and the permission requirement. It does not mention whether repeat uploads create duplicates or how failures are reported, which keeps it short of a 5.

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?

Four short sentences with zero filler, front-loaded with purpose, then constraint, then effect, then intended use case. Every sentence contributes a fact an agent needs to call the tool correctly.

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 no output schema, the description covers the essential gaps: size limit, encoding format, permission prerequisite, and observability of the result. Annotations carry the safety profile and the schema carries all six parameters, so nothing material is left unstated.

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, but the description contributes meaning the schema lacks: the 10MB decoded limit on content_base64 and the "no data: prefix" encoding contract, both of which prevent common invocation errors. It does not clarify the upload_type category semantics, leaving that parameter's purpose thinner.

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 opens with a specific verb and resource ("Attach a file to a board task") and immediately clarifies the mechanism (base64 content) and downstream visibility. It implicitly distinguishes itself from siblings such as list_task_files and list_board_files, which are read operations, so an agent can tell what this tool is for without opening a 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?

It gives clear context for when to use it ("artifacts an agent produces or handles: images, documents, exports") and a hard prerequisite (board membership). What is missing is an explicit when-not or a pointer to an alternative path for files that exceed the limit, so the guidance is strong but not exhaustive.

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