Check whether the current executor thread is parallel

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered structurally. The description adds value with "without changing scheduler state," "Requires: active-client," and "cost=medium," but these are terse and formulaic rather than rich behavioral context.

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 purpose first, which is good. But it is fragmented into boilerplate key-value fragments (Phase/cost/idempotency/Safety) and closes with a generic "inspect tool-schema" instruction that adds little; a tighter sentence would carry the same 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?

For a simple read-only boolean check with one optional parameter and full annotations, the description covers return type, non-mutation, prerequisites, and failure handling. No output schema is needed since it returns a boolean. It is nearly complete, with only sibling routing left out.

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%, so the single threadContext parameter is fully documented by the schema (optional, server default on omission). The description merely restates the signature ({ threadContext: number? }) without adding meaning, so the baseline 3 applies.

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: calls isparallel/is_parallel and returns a boolean without changing scheduler state. An agent can tell what it does and that it is non-mutating. However, it does not differentiate itself from any sibling, so it falls short of a 5.

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?

"Phase: observe" and "Requires: active-client" give implied context for when the tool is applicable. There is no explicit when-not or named alternative among the many sibling introspection tools (e.g. is-c-closure, is-readonly), leaving selection largely to inference.

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