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

With no annotations, the description carries the behavioral burden. It discloses what is returned (coverage level, sources, cadence, canonical key) and adds an important reliability trait: 'Since.dev answers none honestly rather than guessing.' This goes beyond a generic check description, though it does not address potential side effects or auth.

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?

Two sentences with no fluff. The core purpose and usage timing are front-loaded, followed by a compact list of return values and a valuable honesty caveat.

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 the return payload and the relationship to verify_facts, but it omits parameter semantics entirely and there is no output schema or annotations to compensate. An agent can infer parameter values only from enum names, which is insufficient for a 3-required-parameter tool.

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 compensate for parameter meaning. It does not explain what subjectType, subject, or aspect refer to, nor how to choose values. The enum values are present in the schema, but their semantic significance is left to inference.

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 opens with a specific directive: 'Ask whether something can be watched at all, BEFORE building on it.' This clearly identifies the tool as a feasibility check and distinguishes it from siblings like subscribe or verify_facts by stating it returns the canonical key needed for verify_facts.

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 says to use it 'BEFORE building on it,' which is clear timing guidance. It also ties the output to verify_facts, implying the workflow. It does not explicitly state when not to use it or name alternative tools, but the context is strong.

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