Project thumbnail

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

Goes well beyond the annotations (readOnly/idempotent/destructive are already declared) by disclosing performance profile ('Instant and offline, IlluGen not needed'), a real accuracy caveat (can be outdated or missing for server-edited projects), and the failure shape ('{thumbnail: null, hint}'). This is exactly the supplemental context annotations cannot carry.

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-loaded with the core behavior, then tradeoffs, then return shape – efficient overall. The standalone 'Read-only.' line repeats what readOnlyHint=true already conveys, a small redundancy that keeps it from a 5.

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?

With no output schema, the description correctly documents both success and empty-case returns (JPEG vs {thumbnail: null, hint}), covers why the result may be stale, and gives the remediation path. Nothing needed to call this single-parameter 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?

Single parameter with 100% schema description coverage, where the schema already defines 'path' as the absolute path of the .illugen project file. The description adds no format, resolution, size, or edge-case semantics for the parameter, so the baseline 3 applies.

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 and resource: 'Returns the preview image IlluGen embedded in the project file at its last save.' It immediately distinguishes itself from the visually similar siblings by naming project_screenshot and project_render as the current-state alternatives.

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?

Explicit when-to-use context with named alternatives: it says the thumbnail can be outdated for projects edited through this server, and points to project_normalize to refresh it or project_screenshot/project_render for current state. The condition that selects each alternative is stated, not implied.

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