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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering safety. The description adds the behavioral traits of listing 'most recent' jobs and including a count of running jobs, which is useful context beyond annotations. It doesn't describe pagination or output format, but for a read-only list tool with safety covered by annotations, this is adequate.

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 with no wasted words. It front-loads the core action ('List the most recent render jobs') and follows with the extra value (count of running jobs) and the use case. Every word earns its place, making it highly efficient.

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 tool with no parameters and annotations covering safety, the description provides the essential information: it lists recent jobs and reports the running count. It clearly states what the tool returns and the intended use case. Without an output schema, this is sufficient for an agent to decide when to invoke it. The lack of pagination details is not a gap for a list tool of this type.

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?

There are zero parameters, and the schema coverage is 100% (empty schema). The baseline for 0 parameters is 4, and the description adds no parameter-specific information because none is needed. It does not repeat schema content, so a 4 is the correct baseline.

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 the verb 'List' and the resource 'render jobs', and adds the specific detail that it also returns the number of currently running jobs. This immediately distinguishes it from 'get_job' (single job) and other list tools by specifying the domain (render) and the added running-count feature.

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 includes 'so you can report on or resume in-flight work', which gives a clear context for when to use it. However, it does not explicitly mention alternatives or when not to use it (e.g., 'use get_job for details on a single job'). It provides the purpose but stops short of explicit routing, so a 4 is appropriate.

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