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

Annotations already establish the safe read profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), and the description adds real behavioral context beyond them: both objects are closed sets so unknown keys/out-of-range values are rejected with feedback, caption fields inherit from caption_preset rather than having their own defaults, and color fields accept any CSS string. It stops short of describing output shape, but that is a minor gap given annotations cover safety.

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 purpose, return shape, and call-order directive are front-loaded, and the Notes block is broken into scannable bullets that each carry distinct information (closed-set rejection, field vs additional_fields, default inheritance, logo exclusion). It is somewhat long, but no sentence is filler.

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?

There is no output schema, so the description must explain the return value, and it does so thoroughly (per-setting fields, types, enum values, bounds, units, defaults). Combined with zero parameters and full annotation coverage, nothing an agent needs to call this discovery tool correctly is 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?

With zero input parameters, the baseline of 4 applies. The description instead characterizes the returned field metadata (type, values, min/max, unit, default, description), which primes the agent for what it will receive, though this is arguably output semantics rather than parameter semantics.

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 names a specific verb (describe) and resource (nested agent settings), and explicitly scopes what it covers: composition_parameters and caption_style_overrides. It also distinguishes itself from siblings by tying the call sequence to create_agent/update_agent, so an agent can tell it apart from list_caption_presets or search_docs.

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?

It gives an explicit directive: 'Call this BEFORE setting either object so you use real field names and valid values.' It further routes the agent away from expecting a logo field here, naming the logo-upload tools as the correct path instead, which is exactly the when-not guidance the dimension asks for.

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