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

Annotations already declare readOnly, idempotent, non-destructive, so safety is covered. The description adds real behavioral detail beyond them: which returned fields are optional (description and unit may be absent) and that the decoded series name is capped at 1024 UTF-8 bytes, which matters for how the call can be made.

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?

One dense sentence front-loads the useful content (what is returned) before the constraint and REST path. The REST operation line is minor filler but non-redundant; nothing is repeated from schema or annotations.

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?

With an output schema present, the description needn't detail return shape, yet it usefully previews the fields and flags which are optional. Annotations cover the safety profile. For a single-parameter read tool this is essentially complete, short of guidance on behavior for unknown series names.

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%, but the schema itself carries pattern (^[a-z0-9_]+$) and examples, so the naming format is discoverable. The description compensates partially with the 1024-byte decoded-name limit, but adds nothing about resolution behavior when a series does not exist.

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 ('Returns') and enumerates exactly what metadata comes back for a series: description, indexes, nullable indexes, value type, unit. This is clearly distinct from value-fetching siblings like get_series or get_series_latest, though the description never names those siblings to make the distinction explicit.

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?

There is no explicit when-to-use guidance or exclusion versus get_series, get_series_latest, list_series, or search_series. The scope ('for the specified series') implicitly signals this is a per-series metadata lookup, but the agent must infer the choice from the return fields listed.

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