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

The annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds information the annotations do not: the result shape (count plus id/name/image URL per item), ordering guarantees, and the fact that MCP Apps clients render each call as a card, which tells the agent the call has a visible side effect for the user.

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?

Three short sentences, front-loaded with the filtering contract, then the return shape, then the client-rendering note. Nothing is redundant; only the phrase "the still's URL" is slightly opaque.

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 three-optional-enum read tool with no output schema, the description covers filtering logic, return fields, ordering, and the UI-card behavior in MCP Apps. An agent has everything needed to call it and interpret the response.

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 the enum parameters are already documented. The description nonetheless adds meaning beyond the schema by establishing AND semantics across the three filters and a minimum-one-filter rule. That rule sits slightly awkwardly against the schema declaring zero required parameters, which keeps it from a 5.

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-plus-resource framing and states the retrieval semantics precisely: only exercises matching *every* filter are returned, and results come back in the library's order. It does not explicitly distinguish itself from the sibling find_exercise, which is the main thing keeping it below a 5.

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 clause 'matching every filter given, at least one' implies a minimum-one-filter usage rule, which is real guidance about how to call it, but there is no statement of when to prefer this over find_exercise or show_workout, and no exclusions.

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