fail_step

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

With no annotations, the description carries the full burden. It discloses that step_id can be inferred from an environment variable and that the return indicates retryability or permanent failure. It does not mention side effects or destructive nature, but is adequate for a step failure report.

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 description is concise with a front-loaded purpose, followed by a structured Args and Returns section. Every sentence is informative and earns its place.

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?

The description covers both parameters, the return value, and environment variable inference. Given the presence of an output schema (which may detail return values), this is sufficiently complete. It could mention prerequisites or side effects, but is solid overall.

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?

The schema has 0% description coverage, so the description must compensate. It explains both parameters: step_id (your step ID, inferred from env) and error (what went wrong), and also describes the return value. This is excellent semantic addition.

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?

The description clearly states 'Report that you cannot complete your step', using a specific verb and resource. It distinguishes itself from siblings like complete_step (success) and abort_branch (branch-level abort).

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 description implies usage when a step cannot be completed. While it does not explicitly list alternatives, the context of siblings and the purpose make it clear. A slight improvement would be an explicit when-not statement.

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