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

Annotations already declare a non-read-only, non-idempotent, non-destructive write. The description adds real value beyond them: a concrete rate limit (20 new guests per network per hour) and cookie-based reuse behavior (an existing browser gets its guest from the `mr_guest` cookie). It never explains the failure mode when the cap is hit, which keeps it short of a 5.

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 short sentences, but the opening fragment "Creates a guest mr_…" is clipped and reads as broken text rather than a clean front-load. The rate limit and cookie behavior are the highest-value parts and they land after the garbled lead.

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?

There is no output schema, so the description bears some burden for describing what comes back; it only hints at persistence via the `mr_guest` cookie and never says what the created guest object contains or what happens on rate-limit failure. Adequate for a zero-param tool, but not fully self-contained.

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?

Zero parameters, so the schema carries everything and the baseline is 4. The description's "Asks for no e-mail" helpfully reinforces that this call takes no arguments, which matches the empty schema.

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?

States a specific verb ("Creates") and resource ("guest"), and the rest of the sentence clarifies scope. Sibling tools are all listing/feed/index oriented, so no guest-related alternative exists to disambiguate against, but the operation is unmistakable. The truncated "mr_…" fragment is noise but doesn't obscure the purpose.

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?

"Asks for no e-mail" implicitly tells the agent no input is required, and the rate-limit line implies this is a lightweight anonymous identity. However, there is no explicit when-to-use statement, no prerequisite, and no named alternative, so usage is only implied.

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