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

Annotations already declare a safe, idempotent, closed-world read, so the safety burden is lifted. The description adds genuinely useful behavioral context beyond them: access is gated on a Watch subscription with a key, and the output is scoped to a fixed weekly comparison window rather than an arbitrary range. It does not discuss rate limits, latency, or what happens on the very first run when only one check exists.

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, front-loaded with the audience/access condition before the content list, and every clause contributes something. It is dense with product vocabulary and the opening fragment ('OperStack Watch subscribers, with their key.') reads as a prerequisite label rather than a sentence, which costs it the top score.

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 no output schema, the description must describe the return, and it does so concretely across three result categories, which is the main thing an agent needs. Remaining gaps are the multi-site default behavior and the failure mode when fewer than two weekly checks exist.

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 is one optional parameter with 100% schema coverage, so the schema already carries the meaning and the baseline of 3 applies. The description adds nothing about the site selector beyond what the schema description ('Only if you watch more than one site') already states.

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 names a concrete deliverable — the movement between the last two weekly checks — and enumerates its contents (named-answer counts in ChatGPT and Perplexity, share against each competitor, buyer questions where the subscriber was named or dropped). That is far more specific than a restatement of the name. It stops short of 5 because it never contrasts itself with close siblings such as my_visibility or compare_sites, so the agent must infer that this is the delta view rather than the current-state view.

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?

Usage is implied by the framing: it is for OperStack Watch subscribers, and it reports the diff between two weekly checks, so an agent can infer it answers 'what moved this week'. However, there is no explicit when-to-use statement and no routing against alternatives like my_visibility or who_instead, so selection still relies on inference.

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