series_metadata

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

Annotations already declare readOnlyHint=true and the '[READ]' prefix aligns, so the safety profile is consistent rather than contradicted. The description adds genuine value beyond annotations by disclosing the return envelope (returned/limit/truncated) and warning that truncated=true means partial results that must not be treated as complete.

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?

Front-loads the one-line purpose, then uses structured Args and a Returns paragraph. Every sentence earns its place, including the truncation warning, with no redundancy.

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 no output schema, the description supplies the missing return-value envelope and truncation semantics, plus full parameter documentation for a 0%-coverage schema. Nothing 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 0%, so the description must carry the burden, and it documents all four parameters: match as a PromQL selector with a concrete example, start/end as RFC-3339 or unix timestamps, and target as a config name defaulting when omitted. It does not explain default time-range behavior when start/end are absent, leaving a small gap.

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 (retrieve) and resource (series/label-set metadata) scoped to a PromQL selector, which clearly separates it from sibling query tools like instant_query, range_query, and label_values. An agent can identify the tool's role without opening the 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?

The description gives truncation-handling guidance ('narrow the selector or raise the limit'), which is useful operational context, but it never states when to choose this tool over alternatives such as label_values or instant_query. Usage is implied rather than explicit.

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