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

Annotations already declare readOnly, idempotent, and non-destructive, so safety is covered. The description adds genuinely useful context beyond that: no full record telemetry or block-header hash is returned, and the fingerprint is explicitly not a verification receipt, which prevents an agent from over-trusting the output. Only pagination/limits are unaddressed, and an output schema exists to cover return shape.

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 tightly packed sentences: capability first, then the important negative constraints, then sibling routing. Nothing is redundant with the name or title, and the exclusions are placed after the purpose so the agent reads the core function first.

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, idempotent, two-parameter lookup with an output schema, the description covers purpose, routing, and the semantic caveat that the fingerprint is not a proof. Nothing an agent needs to call this 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 coverage is 100% and the schema already documents the format enum in detail, so baseline is 3. The description adds a small amount beyond the schema by confirming that target accepts height, ISO date, or a '..' bounded range, mapping the abstract 'target' field to concrete intent.

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?

States a specific verb (fetch) and resource (compact source-record fingerprints and metadata) scoped to an indexed stratum height, date, or bounded date range. The scope is precise enough that an agent can distinguish it from stratigraphy.get, get_range, and list without opening any schema.

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?

Explicitly names three alternatives and the condition selecting each: use stratigraphy.get when full data is needed, stratigraphy.get_range for contiguous multi-record summaries, stratigraphy.list for catalog discovery. This is textbook when/when-not routing.

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