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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower, and the description still adds real behavioral context: values come from the nearest persisted point with its date and basis, and gaps are flagged ('none HEY did not persist', 'Never a cause'). This discloses data provenance and an important limitation beyond the annotations.

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 purpose is front-loaded, which is good, but the body is a single dense run-on held together by parentheticals and semicolons, and the trailing fragments ('none HEY did not persist. Never a cause.') are terse to the point of ambiguity.

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?

There is no output schema, so the description properly enumerates the returned categories, and it covers the date-range constraint. Combined with the all-required 3-param schema, an agent has enough to call it correctly, with only the sibling-routing choice left 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 only 33% (just the slug), so the description carries the burden for from/to — and it does, specifying the YYYY-MM-DD format and the 400-day maximum span. That is genuine added meaning not present in the schema for those uncommented 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 states a specific operation (a before/after diff for one project between two dates) and enumerates what's included: releases, status, Build Momentum, valuation and liquidity, and recorded changes. The 'one project' scoping implicitly distinguishes it from compare_projects, but the differentiation is never made explicit.

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 the key eligibility constraint ('at most 400 days apart') and the required date format, which is useful usage guidance. However, it never says when to reach for this tool versus compare_projects, get_project_snapshot, or get_project_timeline — the choice is left to inference.

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