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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds value by specifying what 'full metadata' includes (all sized image URLs, photographer name/URL, dimensions, alt text), which is beyond the annotations. No contradictions detected.

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 that front-loads the verb and resource, immediately stating what the tool does. It lists the metadata components efficiently without fluff, earning every word.

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?

For a tool with one simple parameter and an output schema present, the description is fully sufficient. It explains both the input (numeric id) and the output contents, while the output schema handles detailed return structure. No gaps in context remain.

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 0%, so the description must compensate for parameter meaning. It says 'by numeric id', which reinforces the schema's number type, but adds no extra semantics like where the id comes from, valid ranges, or format. With only one parameter, the tool description's mention of numeric id is minimal but not entirely absent, so a 3 is appropriate.

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 the specific verb 'Fetch' with the resource 'full metadata for a single Pexels photo by numeric id', clearly distinguishing it from sibling tools like photo_search and photo_curated. It enumerates the metadata contents (all sized image URLs, photographer, dimensions, alt text), making the tool's purpose unambiguous.

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 clearly implies usage when you have a numeric photo ID and need full metadata, but it does not explicitly mention alternatives like photo_search or photo_curated for discovering photos. There are no exclusions or when-not-to-use scenarios, but the context is clear enough for selection.

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