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

With annotations already declaring not-readonly, idempotent and non-destructive, the description still adds important semantics: 'Replace' signals full-replacement rather than partial patch (omitted fields are reset), and the version instruction discloses optimistic-concurrency failure behavior. It does not explain auth requirements beyond ownership or what the response contains.

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 action and scoped by the ownership qualifier, followed by the one non-obvious operational requirement. No filler.

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 an 8-parameter mutation with no output schema, the description is adequate but thin: it omits that omitted fields (name, body, tags, metadata) reset to their defaults under full-replace semantics — a meaningful gotcha — and says nothing about failure modes beyond the version check already covered by the schema.

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?

Schema description coverage is 100% and every parameter (including op_key's retry semantics and expected_version) is documented in the schema, so the baseline is 3. The description's 'Pass the version you last read' merely restates the schema's expected_version text without adding format or edge-case detail.

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 ('Replace') and resource ('space') plus an ownership constraint ('you own'), which distinguishes it from create_space and join_space. It does not differentiate itself from the other update_* siblings (update_agent, update_claim), but the purpose is unambiguous.

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 'a space you own' — you must be the owner — and the second sentence tells the caller to supply the last-read version. There is no explicit when-to-use vs. an alternative (e.g. patch vs. full replace, or when to use create_space instead).

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