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

The annotation destructiveHint=true already flags the mutation risk, so the bar is lower. The description adds useful behavioral context in 'Only provided fields are changed', clarifying this is a partial update rather than a full overwrite. It does not, however, explain what makes the operation destructive (the tags parameter replaces the entire tag set, per the schema), nor does it mention permissions or reversibility.

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, front-loaded sentences with no padding: purpose, partial-update behavior, then the underlying REST endpoint. The endpoint reference is mildly redundant for tool-invocation purposes but is plausibly useful for an API-aware agent, so only a minor deduction.

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 three-parameter mutation tool with no output schema and only a destructiveHint annotation, the description is adequate but not complete: it omits that the tags parameter replaces (rather than merges) existing tags, says nothing about required permissions, and does not describe the response, so an agent must infer the destructive scope from the schema.

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 100%, so the schema already documents id, name (max 64 chars), and the tags replacement semantics, making the baseline 3 appropriate. The description only restates the mutable fields and adds no format or syntax detail beyond what the schema provides.

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 (update) and resource (a live instance) plus the exact mutable fields (name and/or tags), which cleanly separates it from read-oriented siblings like lambda_get_instance and lifecycle siblings like lambda_restart_instances and lambda_terminate_instances. The only gap is that it does not name a competing sibling as an explicit alternative.

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?

'Update a live instance's name and/or tags' plus 'Only provided fields are changed' implies when the tool is applicable and signals partial-update semantics, which is genuine guidance. However, it states no prerequisites, no permissions requirements, and no when-not-to-use conditions relative to alternatives, so usage is only implied.

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