emacs_ediff_3way

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

With no annotations provided, the description carries the full behavioral burden. It only says 'three-way comparison of files', which implies a read-only diff operation, but does not disclose whether it launches an interactive Ediff session, modifies files, returns a diff, or has any side effects. This is a significant gap for a tool with no annotation support.

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?

The description is a single, concise sentence that communicates the core function and primary use case with no wasted words. It is front-loaded with the essential purpose and immediately conveys the differentiating 'three-way' aspect.

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?

Given there is no output schema, no annotations, and four parameters, the description is too thin to be complete. It does not explain what the agent should expect as a result (e.g., unified diff text, interactive buffers, exit codes), nor does it provide enough nuance to safely invoke the tool in a merge-conflict scenario where file roles matter.

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 input schema already documents all three required file parameters and the optional format parameter. The description adds no parameter-level detail beyond the schema, but the baseline of 3 applies because the schema does the heavy lifting. The merge-conflict phrasing hints at the roles of 'mine', 'theirs', and 'ancestor' but does not explicitly map to parameters.

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 clearly states a specific action (three-way comparison) on a specific resource (files) and adds the merge-conflict use case. It distinguishes this tool from siblings like emacs_ediff_files and emacs_ediff_buffers by explicitly marking it as three-way and file-based.

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 provides a clear context: 'useful for merge conflicts', which signals when an agent should consider this tool. However, it does not explicitly exclude two-way comparisons or mention alternative tools, so while the usage context is clear, there is no explicit when-not guidance.

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