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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds useful behavior beyond that: compilation validity, syntax error reporting, execution timing, structural analysis, and a 1-credit cost. It does not mention input size limits (20000 chars text / 500 chars pattern) or rate/error behavior, which is the remaining gap.

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 content is dense and front-loaded, with purpose first and cost last. The opening 'Regex Tester: Regex Tester tests...' redundantly echoes the title, which is the only real waste.

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?

Output schema exists, so return values need not be explained, and all five parameters are documented in the schema. The description covers purpose, operations, and cost, which is sufficient for this complexity level; only edge-case behavior such as error handling on invalid patterns is left implicit.

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 100%, so the baseline is 3. The description does add value by enumerating the operation types, which clarifies the vaguely documented 'Operation type' enum-less test_type field, and it implies that 'replacement' applies only to the replace operation, but it never names parameters explicitly or resolves the mismatch between the listed operations and the schema's default of 'test'.

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 and resource (tests regular expressions against input strings) and enumerates the supported operations (match, search, replace, split). It does not name any sibling to distinguish from, but no sibling tool in the list performs regex testing, so the purpose is unambiguous.

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 through the operation list; there is no explicit when-to-use guidance, no prerequisites, and no mention of when an agent should prefer something else. An agent can infer this is the tool for regex work, but the description does no active routing.

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