Structural diff

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds valuable context: it states the tool fails with a 'not a git repository' error outside a git repo, and clarifies the diff is structural rather than textual. This goes beyond the annotations without contradicting them.

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 three sentences with no redundant words. It front-loads the core purpose in the first sentence, then quickly covers prerequisites and a contrast with log. Every clause earns its place.

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 simple tool with one optional parameter and no output schema, the description covers the main functionality, the git prerequisite, and the distinction from log. It does not detail the exact output format, but 'structural diff of nodes and edges' gives a reasonable expectation. The omission is minor given the simplicity.

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 schema has 100% coverage for the single 'since' parameter, describing it as a git ref with default HEAD. The description repeats this ('since, default HEAD') without adding significant new meaning. Baseline of 3 is appropriate since the schema already documents the parameter fully.

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 states a clear verb ('diff') and resource ('nodes and edges'), and explicitly differentiates from text hunks by saying 'grove structures, not text hunks.' It also mentions the git ref parameter. This is specific and distinguishes the tool from siblings like log and show.

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 use case (structural diff against a git ref) and explicitly notes the prerequisite that the project root must be a git repository, including the failure mode. It also contrasts with the sibling log ('log shows who changed what and when'), giving an implied when-not-to-use directive.

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