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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so safety and repeatability are covered. The description adds the default-value behavior and the conceptual output shape, but says nothing beyond the annotations about the return payload detail (an output schema exists anyway) or any constraints. Adequate but modest added value.

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?

A single tightly packed sentence front-loads the operation, then the operand options and default, then the output buckets and the motivating use case. Every clause carries information; nothing is padded or redundant.

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 annotations covering the safety profile and a full output schema covering the buckets' structure, the description supplies everything needed to call it: required operands, the 'current' default, and the diff semantics. Minor gaps remain around prerequisites (must snapshots already exist?) and any ordering/limit behavior.

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% and all three parameters (base, compare, project_id) are fully documented in the schema, including the 'current' sentinel and UUID formats. The description merely restates base/compare semantics, adding essentially no meaning beyond the structured fields — the 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 ('Diff') and resource ('a project') plus the two operands (base snapshot vs. compare state), and enumerates the resulting buckets (ADDED/REMOVED/MODIFIED/UNCHANGED across stories, requirements, interface contracts). No sibling tool overlaps this snapshot-comparison function, so the agent can select it unambiguously.

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?

It gives a clear use context ('the basis for the implement only what changed loop') and documents the default of compare as 'current'. However, it names no alternative tool and offers no when-not guidance (e.g., when to just call get_project_snapshot instead), so routing is implied rather than explicit.

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