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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the agent knows this is a write operation with destructive potential. The description adds a key behavioral nuance: switching to 'custom' is only valid if theme files exist, implying an error condition otherwise. However, it does not disclose the full scope of changes (e.g., immediate impact on live blog, irreversibility, or what happens to the previous theme). Given the annotation coverage, the description provides minimal additional context beyond the condition, so a 3 is appropriate.

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 description is a single sentence with no filler. The primary action is front-loaded, and the conditional for custom themes is placed immediately after the main clause. Every word earns its place, making it efficient and easy to parse.

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?

As a destructive mutation tool, the description is thin given the potential impact. It lacks instructions on verifying the availability of custom theme files (e.g., using list_theme_files), what happens if the theme is invalid or unsupported, or the irreversible nature of the change. While the schema and annotations cover some basics, the description does not guide the agent on safe or correct usage, missing critical operational context for a tool that alters a blog's appearance.

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 both parameters are well described in the schema (blogId references list_blogs, theme_id lists enum values and explains 'custom'). The description enhances this by clarifying that some theme_id values are 'built-in' and that 'custom' requires existing theme files. This adds contextual meaning to the parameter beyond the bare enum, particularly distinguishing 'custom' as special. The description does not elaborate on blogId, but the schema already covers that adequately.

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 clearly states a specific action ('Switch a blog to a different built-in theme or to custom') and identifies the resource (blog theme). It distinguishes this from sibling tools like list_available_themes or update_theme_settings by focusing on the active theme change, not listing or settings. The scope is unambiguous and the verb+resource pairing is precise.

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?

The description provides no guidance on when to use this tool versus alternatives. It implies switching themes but does not mention using list_available_themes to discover options, nor list_theme_files to verify if custom theme files exist before choosing 'custom'. The only condition given is 'if theme files exist', but it does not explain how to check that or what to do if they don't. No exclusions or alternatives are mentioned, leaving the agent without direction on when this tool is appropriate.

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