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

Annotations already declare readOnlyHint=true, so the agent knows this is a safe read operation. The description adds useful behavioral context by indicating the data is current ('right now'), restricted to open vacancies, and includes counts and city breakdowns, which goes beyond the annotation-only picture.

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 a single sentence that front-loads what the tool returns and then attaches the workflow hint. Every clause adds value: the resource, the live-scope qualifier, the count detail, the city detail, and the relationship to list_jobs.

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 zero-parameter, read-only tool with no output schema, the description adequately covers what the tool returns and when to use it. Minor ambiguity remains around what 'cities hiring most' means exactly, but the description is otherwise complete enough for an agent to use the tool correctly.

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 tool takes zero parameters, so the input schema is trivially complete and there is nothing for the description to clarify. Per the zero-parameter baseline, a 4 is appropriate because no additional parameter semantics are needed.

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 states a specific verb and resource: it lists fields of work with open vacancies, includes counts, and notes the cities hiring most. It also distinguishes itself from the sibling list_jobs by framing this as a precursor that supplies filter values, so an agent can clearly tell them apart.

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 gives clear context by saying this is 'useful before calling list_jobs with a field or city filter,' which tells the agent when to invoke it. It does not explicitly state when not to use it or name other alternatives, but the workflow guidance is strong.

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