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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds substantive behavioral context beyond this: the guide is 'authoritative', it explains 'exactly which previous tool produces each ID', and it warns that 'lookalike values must NOT be passed'. This tells the agent what kind of content and constraints the tool returns, which is meaningful additional disclosure.

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?

Two sentences with no filler. The main action ('Return the authoritative Nilyo ID semantics guide') is front-loaded, followed immediately by usage context, and then content scope. Every clause earns its place and the description remains skimmable despite covering many ID categories.

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 read-only reference tool with one optional enum parameter and no output schema, the description covers the resource, when to use it, and what it contains. The main missing piece is how the 'id_type' parameter affects the returned content—whether it filters the guide or is required. This is a notable but non-critical gap given the tool's simplicity and the annotations already covering safety and idempotency.

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 0%, so the description must compensate for the lone 'id_type' parameter. It groups the ID types into human-readable categories ('inbox/contract ID', 'email/thread/folder/attachment ID', etc.), which maps helpfully onto the enum values. However, it never explains the parameter's actual behavior—that passing a specific id_type filters the guide and that omitting it returns the full guide. This is a significant gap given zero schema coverage.

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 opens with a specific verb and resource: 'Return the authoritative Nilyo ID semantics guide.' It makes the tool's function immediately clear and enumerates the ID types covered. However, it does not differentiate itself from the sibling tool 'agent_capability_guide', which is also a guide-style tool, so it falls short of a full 5.

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 states when to use the tool: 'Use this when unsure whether a tool needs a LinkedIn system user ID, public identifier, request ID, ...' This is clear contextual guidance. It does not, however, state when NOT to use it (e.g., when the ID type is already certain) or name any alternative tools, so it does not fully meet the 5-level bar.

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