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

Beyond the annotations, the description adds useful behavioral context: non-supported systems still return the direct applyUrl for human use, the tool answers about the job rather than the key, and authentication is required. These details are not redundant with the readOnlyHint/idempotentHint/destructiveHint annotations.

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?

Three sentences, each earning its place: main purpose, fallback behavior, and alternative-tool routing plus prerequisite. The key scope differentiation is front-loaded and the entire description is free of filler.

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 a rich annotation set and an output schema present, the description covers what is needed to invoke the tool correctly: purpose, scope, job-vs-key distinction, fallback behavior, and authentication requirement. Nothing essential is missing for this level of complexity.

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 provides no description for the single 'id' parameter, so the description must compensate. The text makes clear that the id refers to the job being checked ('this job'), especially by contrasting with key_status. It does not explicitly state the id's source or format, but for a single-parameter check tool, this is sufficient.

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 that the tool determines whether the apply agent can submit an application for a specific job on the user's behalf, and explicitly distinguishes it from key_status by noting this tool answers about the job, not the key. This gives a specific verb, resource, and scope that separates it from siblings.

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 explicitly tells the agent when to use key_status instead: 'For whether THIS KEY may apply at all, call key_status.' It also clarifies the tool's scope and prerequisite ('Needs a key or a sign-in'), making the usage context unambiguous.

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