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

Annotations only cover destructiveHint=true; the description adds the mutation warning ('MUTATES Text-Em-All data'), clarifies that user_id is path-only and never sent in the body, and states the return value. It stops short of saying which fields are destructive or whether partial updates are safe.

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 mutation warning and endpoint, then packs usage details efficiently into a few dense sentences. Slightly information-heavy but every sentence contributes.

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 supplies the key missing pieces: mutation semantics, path-vs-body handling, and return value. It does not cover failure modes or permissions, but is otherwise sufficient to call correctly.

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 the schema already documents user_id, firstName, lastName, and the fields bag. The description largely restates this (PascalCase examples, path-only user_id), adding only marginal meaning beyond the schema baseline.

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 ('updates an existing account user') and pins it to the exact API operation (PUT /v1/account/users/{user_id}). An agent can distinguish it from the sibling add_account_user without opening either schema.

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?

Explains how to use the tool (pass changes via `fields` in PascalCase, user_id goes in the path only, not the body). This is clear operational context, but it never states when to prefer this over a sibling or any prerequisites/permission requirements.

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