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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lower, yet the description adds real substance: nothing is persisted, nothing is deployed, and it discloses the limitation that the handler is not built so deploy may still reject an unserveable return type. That caveat is genuinely non-obvious 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?

Two tight sentences with the core operation and its non-effects front-loaded, followed by one caveat sentence. Nothing is redundant and nothing is padding.

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?

With no output schema, the description correctly carries the return contract ('diagnostics with file and line') and warns about a downstream failure mode. It is close to complete; it does not describe diagnostic severity or error response shape, but nothing essential to invoking it is missing.

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 schema already documents privateKey and the files array in detail. The description adds no parameter-level syntax or format detail, 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 (compile code) and immediately bounds scope with 'without saving or deploying', which cleanly separates it from write_code/change_code and deploy. An agent can identify the operation without opening the schema.

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?

The 'without saving or deploying' framing clearly implies the use case (validate before persisting or shipping) and even explains the payoff relationship with deploy. It stops short of explicitly naming the sibling tools it substitutes for, but the contrast is unambiguous.

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