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

Annotations already establish read-only, idempotent behavior, so the description adds value by disclosing that the result is paginated and filterable by status, category, core/supplementary status, and in-force date. This enriches the agent's understanding of behavior beyond the annotations without contradicting them.

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 sentences, front-loaded with the core purpose, then filters, then a workflow. Every sentence earns its place and there is no redundant restatement of the tool name or title.

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 six-parameter, read-only listing tool with an output schema, the description covers purpose, filtering, pagination, and how to chain with related tools. It is missing some parameter-level detail, but the output schema and workflow guidance make it sufficiently complete for an agent to invoke it 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 only 33%, so the description must compensate. It explains category, core/supplementary, status, and date filtering at a high level, but it does not clarify limit, cursor, or possible values for category and status beyond the schema's lone 'in_force' example. Useful but incomplete.

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 states a specific verb and resource: 'discover which EU instruments are held' and 'find their registry ids and legal status.' It clearly establishes the tool's role in the coverage workflow and distinguishes it from provision-level tools like list_provisions and get_provision.

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?

It gives explicit context for use ('before a coverage question') and a concrete workflow: filter by category, use list_provisions, then get_provision. However, it does not explicitly say when not to use this tool or how it compares to searching siblings like search_legislation, so a small gap remains.

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