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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuine behavior beyond them: a 500ms execution timeout, JavaScript flag semantics, and the return shape ('indexed matches and capture groups'). It stops short of noting limits like the 20000-char text cap or the 50-case test limit.

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?

Four short sentences, front-loaded with the core purpose, followed by return shape, semantics/timeout caveats, and the follow-up action. No filler; every sentence 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?

No output schema exists, but the description states the return contents (indexed matches and capture groups), covers execution semantics, and points to the highlighting workflow. The main gap is not mentioning the size caps that constrain inputs, which matters for a 4-param tool with an array parameter.

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%, so the description must carry parameter meaning. It does explain that 'flags' follow JavaScript semantics and that 'tests' are expected match/non-match cases, which is real added value, but it never explains defaults (flags='g', tests=[]), the maxLength/maxItems constraints, or the required pattern/text relationship.

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 ('Execute a JavaScript regular expression against text') plus the expected-test-case dimension, which no sibling provides. An agent can distinguish this from usesignal_format_json, usesignal_diff_json, and the other converter/encoder siblings immediately.

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 implied by the purpose (test a regex), and it names a follow-on tool (usesignal_open_workbench) for highlighting matches, which is helpful routing. However, it gives no explicit when-to-use conditions or when-not-to-use exclusions relative to alternatives.

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