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

The readOnlyHint annotation already declares the safety profile, but the description adds useful behavioral detail: the exact format of each returned artifact (text vs base64 og.png) and the structure of copy keys (hint plus max). It does not cover file size limits or truncation behavior for large base64 payloads, which keeps it from a 5.

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?

Two dense sentences with the read-only note front-loaded, followed by return contents and then the routing advice. No filler; every clause carries either scope, output format, or usage guidance.

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 carries the return-value burden and does so completely: file formats, base64 encoding, copy key structure, and the schema field are all named. For a three-parameter read tool, an agent has everything needed to call it 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 coverage is 100%, so baseline is 3, but the description adds intent beyond the schema by tying `paths` to a specific workflow ('read them with paths only when you will change the markup'). The `id` and `layout` semantics are already fully handled by the schema text, so the added value is partial rather than comprehensive.

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 opens with a specific action and resource: reading a single starter's files, copy keys, and expected schema. It enumerates exactly what comes back (HTML/CSS/SVG as text, og.png as base64), which distinguishes it from list_starters and start_from_starter 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?

It states plainly when the tool is not needed ('Normally you do not need the files: start_from_starter fills them for you') and the precise condition that selects it ('read them with paths only when you will change the markup'). The sibling alternative is named explicitly.

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