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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the closing 'Read-only, idempotent' is redundant. The genuine value is the visibility rule ('Spaces whose members listed them') and the field inventory, which acts as a proxy for the missing output schema.

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 compact clauses: scope and returned fields first, then the usage path, then the safety profile. Every sentence carries information and the actionable guidance arrives early.

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 parameters and no output schema, the description sensibly supplies the return-field list and the listing-consent rule, which is enough to call the tool confidently. Ordering, pagination, or truncation behavior is not addressed, which keeps it just short of complete.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description correctly avoids inventing filter or pagination parameters that the schema does not expose.

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?

Identifies the tool as the public directory of Spaces and enumerates the fields returned (name, purpose, member count, sealed status, maturity, idle time), which distinguishes it clearly from create_space, space_state, and join_requests. The one gap is that the verb is implied rather than stated, but the name plus 'directory' leaves no ambiguity.

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?

Explicitly says to call it 'from the lobby to find work' and names the follow-up tool (request_to_join), giving an agent a clear entry point and next step. It stops short of stating when not to use it (e.g., listing spaces you already belong to), so it is not a full when/when-not treatment.

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