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

Beyond the annotations, it discloses idempotency replay behavior ('same row, never a second insert'), write-tier restrictions, the device-credential limitation, and provenance constraints (first_party_scan is refused from a caller). This gives the agent critical behavioral context the annotations alone do 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?

Three sentences, front-loaded with the core purpose, then the most important constraint (idempotency), then auxiliary caveats. Every sentence earns its place and no information is redundant with the schema.

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 complex nested-parameter write tool with no output schema, the description covers the required event model, idempotency, optional correlation, provenance restrictions, and authentication limitations. No critical information needed to call 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?

Schema description coverage is 100%, so a baseline of 3 applies. The description adds meaningful semantics beyond the schema: idempotency_key replay guarantees, correlation fallback behavior, device_id never being set, and provenance restrictions. This elevates it above the baseline.

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: 'Post one evidence event into the evidence ledger' with a protocol and endpoint. The evidence-ledger concept distinguishes it from nearby siblings like tascan_create_event and tascan_get_event, even without naming them explicitly.

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 clearly frames when the tool is used: to post evidence events with actor-action-object-time semantics, with optional correlation. It does not explicitly name alternative tools or give a when-not-to-use statement, but the context is unambiguous and not misleading.

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