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

With readOnlyHint=true already declared, the description goes well beyond annotations by disclosing the return semantics: executable join_specs, null when a hop can't be tested, cardinality and verb direction, strength, measured row coverage including blank-key misses, caveats, object systems, and PII fields. It also clarifies that the map never returns data itself.

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 long and dense, but every clause earns its place because there is no output schema to document the returned fields. The core outcome is front-loaded, followed by specifics and usage guidance, though the single run-on sentence structure is heavier than ideal.

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 tool with two parameters and no output schema, the description is unusually complete: it enumerates the return payload, defines ambiguous terms like row coverage and null hops, notes PII exposure, and gives invocation timing. Nothing essential to calling the tool correctly is missing.

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 both parameters at 100% coverage with examples, which sets the baseline at 3. The description adds meaningful behavior beyond the schema: object names are matched in any case, start vs. target direction matters, and output spelling uses the map's own naming.

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 and resource: given start and target objects, it returns the shortest verified join path. It clearly distinguishes route from sibling data-fetching tools by framing it as cross-system navigation (the map as GPS) rather than data retrieval.

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 explicitly says to use the tool before fetching data in the human's own systems and explains what it provides: where to look, by which columns, and how much to trust each step. It does not name sibling alternatives or state when not to use it, but the usage context is clear.

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