history_compare

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

With no annotations, the description carries the full burden and does disclose real behavior: snapshots are written to ./.dotplot/history.json on every report, and comparison is restricted to matching datasets. The first-run empty-state edge case is called out, which is genuinely useful, though the return shape and diff format are never described.

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?

Three short sentences with the core action front-loaded, followed by storage location and the edge case. Well sized, though the closing directive ('say so rather than implying zero change') is agent coaching rather than tool semantics.

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?

The edge-case and snapshot-storage context is valuable, but with no annotations, no output schema, and zero parameter documentation, an agent still lacks the input semantics and result format needed to call this confidently.

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 0% for two required parameters (csv_path, value_event), so the description must compensate and does not. Neither parameter is mentioned or clarified, leaving value_event in particular entirely unexplained.

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 action and object: comparing today's numbers against the last analysis of the same data. It distinguishes itself from siblings by scoping comparison to saved snapshots rather than benchmarks or across-user analysis, though it never names the nearest alternative (compare_benchmark) 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?

Provides a clear precondition for use: only snapshots of the same dataset are compared, so a first run in a new project has nothing to compare against. It stops short of naming alternative tools for the cases where this tool is inapplicable.

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