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

Annotations only cover safety (readOnlyHint, openWorldHint); the description goes well beyond by disclosing the analysis method (static, no install), the classification rules (runtime removals break `node`, type-only removals break `tsc` and are returned separately), and the conservative rename heuristic (only renames the package itself proves). That is exactly the extra context an agent needs to interpret results.

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?

Front-loaded with the core purpose, then qualifiers; every sentence carries information and nothing is filler. The clauses are dense and long, but they earn their length by explaining result categorization.

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 must carry the return semantics, and it does: removed/added symbols, arity changes, provable renames, and separately bucketed type-only removals. Combined with the 'no install required' note, an agent has everything needed to call and interpret it.

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 params (package, fromVersion, toVersion) are documented there, so the baseline is 3. The description adds no syntax, version-range, or format detail beyond the schema.

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?

Names a precise verb+resource: the runtime surface diff of a package between two versions, and enumerates exactly what the diff contains (removals, additions, arity changes, provable renames, type-only removals). It also distinguishes itself from other comparison siblings by scope ('static comparison, with no install required').

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?

Explicitly states when to use it: 'Use before an upgrade, and to explain a break after one.' That covers both the pre-flight and post-mortem context, though it never names a when-not case or points to a specific alternative sibling such as compat or verify.

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