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

Annotations already declare readOnlyHint, openWorldHint=false, and idempotentHint, so the safety profile is covered. The description adds that output format varies by mode (inline diff, side-by-side rows, unified patch), which is useful context, but with an output schema present this is somewhat redundant and no auth/rate-limit/permission behavior is discussed.

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?

Two tight sentences with no filler: the first states what is compared and the available modes, the second states what is returned. It is front-loaded and every clause carries information.

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?

An output schema exists, so return shapes need not be described, and the description still usefully notes the mode-dependent formats. The main gap is the undocumented ignoreWhitespace parameter; otherwise it is adequate for a four-parameter, read-only comparison tool.

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 50% (left and right are described; mode and ignoreWhitespace are not). The description partially compensates by naming the mode values and explaining JSON mode's key-order insensitivity, but ignoreWhitespace is left completely undocumented in both schema and description.

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 (Compare) and resource (two texts) plus the supported granularities (line, word, character, JSON). No sibling tool is a diff tool, so an agent can identify this one unambiguously from the tool list.

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?

Usage is only implied: it lists modes and gives one selection hint for JSON mode ('so object key order does not matter'). There is no explicit when-to-use, when-not-to-use, or prerequisite guidance, leaving mode choice mostly to inference.

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