Latest value of a metric

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

Annotations already provide readOnlyHint=true and destructiveHint=false, and the description adds useful behavioral context by calling the operation 'equivalent to a real-time reading' and specifying the result as 'Latest known value with its timestamp.' This goes beyond the schema and annotations without contradicting them.

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?

The description is compact, front-loaded with the core purpose, and uses short use-case bullets plus a one-line Returns statement. There is no filler; the Args quick-reference is slightly redundant with the schema but not bloated.

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 single-value read tool with no output schema, the description covers what it returns ('Latest known value with its timestamp'), when to use it via concrete examples, and all three arguments. This is sufficient for an agent to select and invoke it correctly alongside the sibling query, aggregate, and list tools.

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?

The Args section restates parameter intent ('Tag filters to target a specific host') and the response format options, adding a small amount of usage context. However, schema_description_coverage is 67%, and the description does not meaningfully extend the schema's richer details such as array-valued tags with logical OR semantics.

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 opens with 'Retrieves the most recent value of a metric (equivalent to a real-time reading)', a specific verb+object that clearly identifies the operation. The use-case examples 'current CPU usage' and 'Latest reading from the request latency metric' further distinguish it from range, aggregate, and list siblings.

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?

Explicit use-case sentences such as 'What is the current CPU usage on server web-01?' tell an agent exactly when this tool is appropriate. It does not explicitly state when not to use it or point to alternatives like kairosdb_query_range or kairosdb_aggregate, so it stops short of full when-not guidance.

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