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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the description goes beyond that by disclosing the result shape relative to a sibling tool and, importantly, the failure-mode behavior: 'An unknown slug returns the closest matches' rather than erroring. That edge-case disclosure is the kind of thing an agent cannot infer from the schema. It does not cover rate limits or ranking caveats, so it falls short of 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?

Five short sentences, each doing distinct work: purpose, trigger, prerequisite, alternative, and return/failure behavior. The core purpose is front-loaded before routing 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?

Even though an output schema exists, the description still tells the agent the rows match 60fps_search_shots minus the source shot and that a bad slug degrades gracefully. Combined with full schema coverage, an agent has everything needed to select and invoke this 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 description coverage is 100%, so slug, limit and response_format are already fully documented with defaults, bounds and enum values. The description adds only that the slug must be obtained via search, not any new semantics for limit or response_format. Baseline 3 is correct when the schema carries the parameter burden.

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 ('Find shots most similar to a given shot') and immediately qualifies the mechanism ('nearest neighbours by embedding'). It explicitly distinguishes itself from the sibling 60fps_search_shots by naming it as the word-based alternative.

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?

Gives the trigger condition ('whenever the user wants shots like a specific one, more like this'), the prerequisite workflow ('call 60fps_search_shots first to get its slug'), and the alternative for a different input type ('To start from words alone, use 60fps_search_shots'). Nothing is left to inference.

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