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

Annotations already cover readOnly, idempotent, and non-destructive behavior. The description adds critical non-obvious lifecycle behavior: the tool is deprecated, no longer refreshed, and will be removed on a specific date. This is exactly the kind of context an agent cannot infer from annotations or the schema.

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 short sentences, with the deprecation warning front-loaded before the purpose and alternatives. Every clause carries useful information: lifecycle status, removal date, replacement tools, and the exact read scope.

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 deprecated, read-only tool with one parameter and rich annotations, the description covers the key decisions: it warns about staleness, names substitutes, and defines the read scope. Return payload details are not supplied, but the annotations and simple schema make this a minor omission rather than a real gap.

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 needed to explain entityId, but it only refers indirectly to 'an entity.' The schema gives type and format, but the description adds no practical guidance about what entityId should identify or how to obtain a valid value.

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 states a specific verb and resource: 'Read canonical facts, aliases, history, and provenance for an entity.' It also distinguishes itself from alternatives by naming discover_daystruct_capabilities and compat_check, so an agent can tell what this tool is for even with the deprecation warning.

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 'For building, use discover_daystruct_capabilities and compat_check,' which is a clear exclusion and hands the agent the correct alternatives. It does not provide a positive 'use this when...' statement, but the deprecation context plus the read-purpose sentence make the intended scope reasonably clear.

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