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

Annotations already declare readOnly, idempotent, open-world and non-destructive, so the safety profile is covered. The description adds context annotations cannot carry: it is free, requires no sign-in, and its output is 'generic' rather than personalized. The one remaining gap is that 'generic' is never made concrete, so the agent cannot predict the shape of the result.

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 tight sentences with no filler; the purpose clause leads, followed by cost/auth facts, then routing and exclusion. Every sentence carries information the agent needs.

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 read-only, no-sign-in evaluative tool with no output schema, the description covers cost, auth, scope and the key exclusion. The only shortfall is that it never characterizes the return — a viability score, verdict, or suggestions — leaving the agent to guess what comes back.

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?

Only one parameter, and the schema already documents it at 100% coverage ('The niche to check, described in a sentence or two'). The description adds nothing about format, length, or what makes a good niche_description value, so the baseline of 3 applies.

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 concrete outcome — determining whether a niche is viable before committing — which is more specific than the title 'Check niche'. It also names the class of sibling it is not (signed-in XcutAI tools for the user's own content). It stops short of saying what the tool actually returns, so it is clear but not fully self-contained.

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?

Explicit when-to-use ('when the user wants to know whether a niche is viable before committing'), explicit when-not ('Do not use for writing unrelated to social media or marketing content'), and an explicit alternative ('for work based on the user's own posts, canvases or brand, use the signed-in XcutAI tools'). This is close to ideal routing guidance.

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