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

With no annotations, the description carries the full burden. It usefully discloses that the operation is non-destructive ('cannot disturb the existing content') and implies the file must already exist, but says nothing about permissions, failure modes if the path is missing, or the returned result.

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?

Two tight sentences, front-loaded with the core behavior, with zero wasted words and the key constraint stated up front.

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?

An output schema exists, so return values need not be explained. However, for a mutation tool with no annotations and 0% param coverage, the description leaves the less-obvious parameters and error/permission behavior unaddressed.

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 0% with 4 parameters, so the description would need to compensate and does not. It never explains path, project_id, or the optional description field beyond the implicit notion of 'content', leaving an agent to infer their meaning from the schema alone.

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 (add/append) and resource (existing file) with a precise scope: content goes to the end. It distinguishes itself from write_file/edit_file by contrast ('without restating what is already in it', 'needs no anchor text') rather than naming the siblings explicitly.

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?

Gives concrete when-to-use examples (bibliography entries, appending a section, extending a log) and implies the alternative by noting it needs no anchor text and won't disturb existing content. It stops short of naming edit_file/write_file as the alternatives an agent should choose between.

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