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

Annotations already cover safety (readOnlyHint=true, openWorldHint=false), so the description earns credit for adding two things they don't: cost ('free') and data freshness ('Live files show the current state until their update period ends'). It still doesn't say what happens to a stale or expired reference, but the added behavioral context is meaningful.

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?

One sentence, front-loaded with the verb and the eligibility condition, with the freshness caveat second. The parenthetical '(free)' is slightly cryptic but is the only questionable token.

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?

With only two fully documented parameters, no output schema and annotations covering safety, the description needs little more than it gives. The remaining gap is what a caller should expect for non-live or expired files, which is left to 'until their update period ends' without resolution.

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%: the ref pattern, its source tools, and the typ enum meanings are all documented in the schema. The description adds nothing about either parameter, so 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 and resource ('Reads a file') with a qualifying precondition ('the account has already opened'), which implicitly separates it from the sibling open_file. It stops short of naming open_file or my_files explicitly, so an agent must infer the split.

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 phrase 'a file the account has already opened' implies this is the follow-up call after open_file, and the list of siblings makes that inference natural. However, no alternative tool is named and no exclusion ('use open_file if not yet opened') is stated.

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