UK Legal Research MCP Server

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

The description adds valuable behavioral context beyond what annotations provide. While annotations indicate read-only, non-destructive, idempotent, and open-world characteristics, the description reveals: 1) default connection to HMRC sandbox, 2) production environment configuration requirement, 3) authentication requirements (OAuth 2.0 via environment variables), and 4) what information is returned (mandate status, effective date, trading name). This significantly enhances the agent's understanding of the tool's operational behavior.

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 efficiently structured with a clear purpose statement followed by important operational notes. Every sentence serves a distinct purpose: the first states what the tool does, the second covers environment configuration, the third addresses authentication requirements, and the fourth specifies return values. No wasted words or redundancy.

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 tool's moderate complexity, comprehensive annotations, complete schema coverage, and existence of an output schema, the description provides excellent contextual completeness. It covers purpose, environment configuration, authentication requirements, and return values - all the information an agent needs to successfully invoke this tool without needing to explain return values (handled by output schema).

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?

With 100% schema description coverage, the input schema already fully documents the single parameter (vrn). The description doesn't add any additional parameter semantics beyond what's in the schema, so it meets the baseline of 3. The description focuses on behavioral aspects rather than parameter details.

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 clearly states the specific action ('Check a business's Making Tax Digital VAT mandate status'), the resource (business's MTD VAT status), and the method (via HMRC API). It distinguishes itself from sibling tools like 'hmrc_get_vat_rate' and 'hmrc_search_guidance' by focusing specifically on MTD VAT mandate status checking.

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 explicit guidance on when to use this tool: for checking MTD VAT mandate status. It also includes important prerequisites (environment variables for OAuth 2.0) and clarifies the default sandbox environment with instructions for switching to production. No explicit alternatives are mentioned, but the specificity of the tool makes its use case clear.

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