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

Annotations already cover read-only, idempotent, non-destructive, closed-world, so the bar is lower; the description adds the calling role requirement and the fact that guests see only granted projects read-only. No mention of pagination or result size, which keeps it from 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?

Front-loads the action and the key output distinction, then supplies the guest definition and auth requirement. The second sentence is dense but every clause (seat, sign-in, read-only scope, role) is load-bearing for correct interpretation.

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 one-param read-only list tool with full schema coverage and annotations, this is nearly complete; it also hints at return content (per-guest project read flag). It does not describe ordering or result limits, which prevents a 5.

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 its schema description coverage is 100%, so the schema fully documents projectId. The description adds nothing about the parameter itself, so the baseline 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?

Specific verb and resource (list the workspace's guests), plus the distinguishing output detail that each guest is marked with project read access. That separates it from list_users and list_invitations without needing the schema.

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?

Gives clear context (guests of this project, requires Administrator or ProjectManager) and points at create_invitation role=Guest for the creation path. It does not explicitly state when-not-to-use or contrast with set_project_guests/list_users, so it falls short of a 5.

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