generate_placeholder

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

With no annotations, the description carries the full burden. It discloses that the tool returns a URL plus HTML and Markdown markup, which is key behavioral output. It doesn't mention limitations like rate limits or external service dependency, but for a simple generation tool this is reasonably transparent.

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 sentences, front-loaded with the core action and service, with no filler. Every phrase adds value: what it generates, what it supports, and what it returns.

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?

Given the rich 9-parameter schema and no output schema, the description's mention of return format (URL + HTML + Markdown) fills a key gap. It lacks explicit guidance on multi-size generation or defaults, but these are covered in schema descriptions, so overall it's complete enough for effective use.

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?

The input schema already documents all 9 parameters with 100% coverage, so the description need not repeat them. The description adds a high-level grouping ('size, colors, text, format, and font') that maps to the parameters but doesn't introduce new semantic details beyond the schema.

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 uses a specific verb ('Generate'), a clear resource ('placeholder image URLs'), and names the service ('placehold.co'). It clearly distinguishes this tool from siblings like image_metadata or extract_og_image, which serve different purposes.

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 implies usage for creating placeholder images and lists supported customization options, giving clear context about when to use it. It does not explicitly name alternatives or exclusions, but sibling names make the distinction obvious enough.

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