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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds substantive context beyond that: the curated corpus size, that only landmark cases qualify, and the degraded fallback mode that returns co-cited cases with related_source "co_citation". It does not describe pagination or result volume directly, keeping it from 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?

The purpose and the primary usage rule are front-loaded in the first two sentences, and the fallback behavior is appended where it belongs. The trailing version tag (MCP22_20260927) is noise that costs a little efficiency.

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?

With no output schema, the description carries the burden of explaining returns and it does name the key returned concept (the doctrinal family) plus a notable result field (related_source "co_citation"). Combined with full schema coverage of inputs, this is nearly complete; only result volume/paging behavior is left unstated.

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 all four parameters are already documented in the schema (including the case_name name+date resolution note and the max_cases default/max). The description adds no parameter-level syntax or format detail over the schema, so the baseline 3 applies.

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 names a specific verb (expand/return) and resource (the doctrinal family of co-cited cases around an anchor authority) and bounds the scope precisely (curated ~1,500 major doctrinal lines, landmark cases only). That is enough to separate it from siblings like get_citing_cases or get_treatment without opening their schemas.

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 when-to-use guidance: "Use when you have one on-point case and need the rest of the line." It also describes the fallback path for a case with no family. It does not explicitly exclude or name alternative siblings (e.g. get_citing_cases), so it falls just short of a 5.

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