env_up

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

Annotations already declare the safety profile (readOnlyHint=false, idempotentHint=true), but the description goes well beyond them: lease-renewal semantics on repeat calls, the instruction to use the returned url/port rather than a conventional port, the readiness field, and a full error-code taxonomy (NOT_A_PROJECT, UNKNOWN_PROJECT, CMD_CHANGED, START_TIMEOUT) with remediation hints (log_tail, rent init, rent sync).

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-loads purpose, then usage, then the error contract. Every clause carries information, though the error-code block is dense and the sentence about url/port could be tightened.

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 usefully documents the returned url/port/readiness and the ok/error shape, which is exactly what an agent needs. The gap is the unexplained profile and lease_minutes parameters.

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 the load, and it only explains one of three parameters (`project`'s default-to-rentctl.toml behavior). `profile` and `lease_minutes` are left entirely to their self-explanatory names and defaults, so compensation is partial.

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 (Start/renew) and resource (this checkout's leased dev environment) plus the return value (its URL). It is clearly distinguishable from env_down/env_ls/env_sweep by contrast, but never names those siblings explicitly, so it stops 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?

Gives concrete when-to-use context: omit `project` to use the checkout's rentctl.toml declaration, and calling it again renews the session lease. It does not, however, state when NOT to use it or point to a specific alternative sibling.

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