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

Adds substantial context beyond the annotations: a 10240-byte total cap, a 413 error on over-cap appends, and the lifecycle detail that saved notes surface at the start of each NEW chat rather than mid-conversation. These are behaviors an agent cannot infer from the readOnly/destructive hints.

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 purpose in the first sentence, then usage triggers, then behavioral constraints and cap. Dense but every sentence carries operational weight; no filler.

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 still covers return semantics ('unless this tool returned success') and failure signaling (413 on over-cap). Combined with the lifecycle explanation, an agent has everything needed to call and report on this tool correctly.

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 single 'block' parameter is fully documented in the schema (100% coverage), setting the baseline at 3. The description adds content-style guidance ('Markdown is encouraged; keep entries terse and factual (preferences, project context, references)'), which meaningfully shapes what to put in the block.

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 and resource: 'Append a block to the calling user's persistent agent memory.' The additive semantics clearly set it apart from agent_memory_replace by nature, but the description never names or routes against that sibling, so it stops short of full differentiation.

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?

Gives explicit when-to-use triggers ('remember X', 'save this', 'note for next time'), a when-not clause ('Do not auto-update on ordinary messages'), and a mandatory same-turn ordering rule. This is exactly the routing guidance an agent needs.

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