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

Annotations indicate destructiveHint=true and readOnlyHint=false. The description adds that it consumes requests or credits, which is consistent with a non-read-only operation. However, it does not clarify whether the original lyrics are modified or if costs are reversible. No contradiction with annotations, but more detail on behavior would improve transparency.

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 extremely concise with two short sentences. It front-loads the core action and immediately provides the cost trait. Every sentence is necessary and no filler is present.

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?

The description is adequate for a simple tool with an output schema (so return values are documented elsewhere). It covers the main function and cost, but given the large number of sibling tools, more contextual guidance would be beneficial. Still, it is complete enough for an agent to understand the basic purpose.

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 coverage is 100%, with both parameters ('lyrics' and 'prompt') described clearly in the schema. The description adds no additional meaning beyond what the schema already provides, so baseline score of 3 is appropriate.

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 clearly states the action ('Extend Wubble lyrics') and the resource cost ('Consumes Wubble requests or credits'). It distinguishes from siblings like 'wubble_generate_lyrics' which creates new lyrics, but does not explicitly differentiate from 'wubble_extend_song' or other similar tools.

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?

No guidance on when to use this tool versus alternatives. The description only states what it does without providing context for appropriate usage, such as prerequisites or when to prefer it over other lyric-related tools.

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