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

Annotations cover the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false), but the description adds the genuinely important behaviors beyond them: partial-update semantics ('only fields you pass change'), empty-string-clears-field behavior, and especially the two-step preview/confirm_token flow. That confirmation protocol is essential and is not derivable from annotations.

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 purpose, then the mutation semantics, then the critical two-step warning. The field enumeration is somewhat redundant with the schema, but the sentences carrying the unique information (clearing, sibling routing, confirm flow) are well-placed and earn their space.

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 and zero required params, the description supplies the partial-update model, clearing behavior, sibling routing, and the confirm_token protocol an agent needs to call it correctly. Only the shape of the preview response is left implicit, which is a minor gap given no output schema is defined.

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%, so every parameter (including confirm_token) is already documented in the schema. The description restates the field list and the empty-string-clears rule, adding marginal value rather than syntax or format detail beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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+resource ('Edit your profile') and enumerates exactly which fields are editable (displayName, bio, location, socials), so the scope is unambiguous. It also explicitly carves out what it does NOT touch (photos, handle) and names the sibling that handles those, letting an agent distinguish it from set_username and update_bottle without opening schemas.

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: use it to change profile text fields, and it routes handle/photos to set_username as the alternative. It also prescribes the two-call confirmation protocol. It stops short of a broader when-not statement, but the routing is explicit enough that an agent won't pick the wrong sibling.

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