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

Adds substantial context beyond the annotations: authentication is required, open state persists per user across MCP sessions with last-open-wins semantics, and callers using per-request sessions need not re-open after auth(confirm_login). It also documents return values (kind, web URL, UUID) and the team defaulting behavior. It does not explain why destructiveHint=true (what closing a session loses or whether create is reversible), leaving one annotation unexplained.

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 summary sentence followed by per-action bullets, which is well suited to a multiplexed tool. Each bullet carries actionable information, though the open_file bullet is dense and could be split so the sibling routing is easier to scan.

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 three-action multiplexed tool with a generic envelope schema and no output schema, the description covers prerequisites, defaults, return values, session persistence and auth. The only minor omission is what close_file returns, which an agent is unlikely to need.

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 input schema is only a generic action/params envelope, so the description carries essentially all parameter meaning: it names file_id, file_name, team_uuid and kind per action, states kind defaults to GRID with DOC/SLIDE alternatives, and explains that an omitted team_uuid falls back to the user's first team. This is meaning the schema alone cannot provide.

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 opening sentence names a specific domain (file management) and enumerates the three concrete actions: create a file, open a file to start an editing session, close a session. It is clearly different from the sibling files_read. It loses a point because bundling a non-mutating session-open under a tool named 'files_write' slightly blurs what the tool really is.

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?

Strong routing: after open_file it explicitly tells the agent to use read_data/write_data for spreadsheets, doc_read/doc_write for documents and slide_read/slide_write for presentations, and it states the prerequisite that a file must be opened before editing. It does not explicitly state when to prefer files_write over files_read, but the read/write split is obvious from the action list.

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