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

Even though annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, the description adds crucial behavioral context beyond these: it explicitly states that 'text' is always null and 'text_extracted' is always false because the full text is PDF-only. This prevents the agent from expecting or trying to use text fields. It also lists the exact return fields, something the output schema does not provide.

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, well-structured sentence that front-loads the core purpose and identifying mechanism, then details the return fields and the critical caveat about PDF-only text. Every clause earns its place; there is no fluff or repetition of annotation content.

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 single parameter, no output schema, and strong annotations, the description is complete. It explains the input format, the return content, the PDF-only limitation, and how to access the actual judgment. An agent has everything needed to invoke this tool correctly without any additional lookup.

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 schema already documents the single 'slug' parameter with 100% coverage, so the baseline is 3. The description adds value by explaining where the slug comes from (search_ni_decisions or a judiciaryni.uk URL), which helps the agent understand how to obtain valid input. This goes slightly beyond the schema's static examples.

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 ('Get'), a specific resource ('one Northern Ireland judicial decision'), and the exact identifying mechanism ('by its judiciaryni.uk slug'). It even names the sibling tool 'search_ni_decisions' as a source for slugs, making it easy for an agent to distinguish this fetch-by-slug tool from the search tool.

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 provides clear context for when to use this tool: when you have a slug from search_ni_decisions or a judiciaryni.uk URL. It does not explicitly list exclusions or alternatives, but the main alternative (search_ni_decisions) is implied and the usage scenario is clear enough. It also gives guidance on handling the PDF-only output ('use pdf_url to read the judgment').

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