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

The description correctly signals a mutating side effect ('or create'), which is consistent with readOnlyHint=false and non-destructive. It adds that resulting knowledge 'uses your existing private account scope,' which is real context beyond the annotations. It does not say what happens on an existing space, whether creation is idempotent, or what is returned.

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 short sentences, front-loaded with the return-or-create behavior and followed by the scope note. Every clause carries information and nothing is padded.

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 an output schema present and no parameters, the description need not explain return values. It covers the key behaviors: this may create, and it is bound to the caller's private scope. Only the idempotency/existing-space case is left unstated, which is a minor gap.

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; baseline 4 applies. The mention of 'your account's' scope correctly implies identity comes from the caller, not from an argument.

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 specific verb pair and resource: 'Return or create your account's personal private Space.' It distinguishes this from private_space_create and private_space_get by scoping to 'your account's personal' space, though it never names those siblings explicitly.

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 only implied: 'personal' and 'your account's' suggest this is the entry point for one's own space rather than an arbitrary space lookup. There is no explicit when-to-use, when-not-to-use, or reference to private_space_create/list/get as alternatives.

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