Set user meta

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

The description goes well beyond the annotations (destructiveHint=true, readOnlyHint=false): it discloses that all stored values of the key are replaced, that no undo point is recorded, that backslashes are stripped, what the return payload contains, and the full refusal list. This gives the agent concrete consequences the annotations alone cannot express.

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?

The core destructive behavior is front-loaded in the first sentence, followed by refusals, auth, edge behaviors and return value. It is dense and semicolon-heavy but nearly every clause carries operational information.

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 mutation tool with no output schema, the description covers preconditions, refused inputs, side effects (no undo), value normalization, and the return shape (updated, user_id, key). Nothing an agent needs to call it correctly appears to be missing.

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 coverage is 100%, so the schema already documents key sanitization, array serialization and the empty-string default. The description adds value semantics not in the schema (WordPress strips backslashes), which raises it above the baseline 3.

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 (create or overwrite) and resource (one user meta value), and clarifies the destructive semantics of replacement. It also names the sibling it is not (role and password are changed by wp_update_user), so an agent can distinguish it from wp_update_user and the post/term meta variants.

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?

Explicit exclusions are given (refused key prefixes, capability/user_level keys, session_tokens, credential-like keys), with the correct alternative named for role/password changes. It also states the permission gate (edit_users) and the failure mode for an unknown user.

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