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

Annotations already declare readOnlyHint=false, destructiveHint=true and openWorldHint=true, so the agent knows this is a mutating operation. The description adds genuinely useful patch semantics ("Only provided fields are updated") and notes that thumbnails are uploaded to a project CDN, but it does not warn about the destructive/potentially clearing behavior suggested by the empty-string defaults on every optional field.

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 behavioral statement is front-loaded in a single sentence, followed by a compact argument list. The Args block partially restates schema titles, but each entry adds meaning (source of the ID, CDN upload, metadata grouping), so little is wasted.

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?

An output schema exists, so return values need not be described, and every one of the 9 parameters receives an explanation despite 0% schema coverage. The remaining gap is the partial-update versus empty-string-clearing question on a tool annotated as destructive.

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 0% for 9 parameters, so the description carries the full semantic burden and largely succeeds: it explains each field, notes that category_id comes from the list response, that thumbnail is uploaded to the CDN, and that the three thumbnail_* fields write into thumbnail_meta. It does not resolve whether omitting a field differs from sending the schema's "" default, which is the one ambiguity an agent would want resolved.

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 and resource ("Update an existing CMS post category"), which is enough to separate it from the create/delete/list category siblings and from update_cms_post. It stops short of naming any sibling explicitly or stating scope limits, so it is clear rather than exemplary.

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?

There is no guidance about when to use this tool versus create_cms_category, delete_cms_category, or update_cms_category's create counterpart; the only usage-adjacent statement is "Only provided fields are updated." No prerequisites, no when-not conditions, no alternatives named.

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